There’s a story that many scientists tell about the evolution of human skin color.
The story goes roughly like this:
In the beginning, our ancestors had dark fur and lightly pigmented skin. This was perhaps six million years ago? Over time, our ancestors lost their fur and needed darkly pigmented skin to protect themselves from the harsh light of the sun.
Later, some people left their ancestral homeland. Migratory humans covered the globe. As humans traveled farther from the equator, they evolved light skin again – otherwise they’d have too little vitamin D.
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In Joanne Cole (author) & Bruce Degen (illustrator)’s The Magic School Bus Explores Human Evolution (which is surprisingly good! You can read my review here), this story is told in a single panel.
Variants on this story percolated through the scientific literature for years, but the version above is derived largely from the work of anthropologists Nina Jablonski & George Chaplin. In their article “The Evolution of Skin Coloration,” they write that “As hominins migrated outside of the tropics, varying degrees of depigmentation evolved to permit ultraviolet-light-induced synthesis of vitamin D.”
This story is often treated as accepted science, even by researchers who describe human evolution from an explicitly anti-racist perspective. For example, in A Brief History of Everyone Who Ever Lived, Adam Rutherford writes that “The unglamorous truth is that there are but a handful of uniquely human traits that we have clearly demonstrated are adaptations evolved to thrive in specific geographical regions. Skin color is one. The ability to digest milk is another, which fits perfectly with the emergence of dairy farming.”
However, this story about the evolution of human skin color isn’t supported by the actual data. Instead, it’s based on Eurocentric misconceptions about what sort of environment and lifestyle are “normal” for human beings.
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Unquestionably, darkly pigmented skin can protect humans from sunlight. And sunlight is dangerous! You should wear sunscreen. (I’m sure that somebody has told you this already.)
But the benefits of light skin have been vastly overstated by (light-skinned) researchers. And a quick glance at the data is enough to demonstrate the major flaws in the evolutionary story I described above.
That same page of The Magic School Bus Explores Human Evolution includes a world map with a (again, surprisingly accurate!) depiction of the paths that ancient humans took to populate the planet.
Looking at those red arrows, you’ll see several occasions when groups of humans migrated farther from the equator. The people who settled in France, Korea, and Patagonia had all reached similar latitudes. (As did the humans who settled in New Zealand, but they only arrived about 800 years ago, which probably isn’t enough time to expect dramatic shifts in skin color. Especially given the likelihood of continued gene flux across latitudes – by the time anyone reached New Zealand, people were probably traveling to and fro by boat often, rather than forming an isolated community.)
If the above story about the evolution of human skin color were correct, we’d expect that indigenous people from France, Korea, and Patagonia would all have similar skin color. Indeed, artist Gail McCormick worked closely with Jablonski & Chaplin to create a cut-paper map depicting the indigenous skin color that their story predicts for various regions.
But this map doesn’t match the skin color we actually see from humans across the globe. The indigenous people of France evolved lightly pigmented skin. The indigenous people of Korea, Patagonia, and North America did not.
Jablonski & Chaplin arrived at their conclusion because they considered very few human populations; Figure 4 from their paper, which I’ve included below, depicts in white all the regions of the globe that they left out of their data set.
Each human migration was another natural experiment: Does migration away from the equator result in lighter skin?
For the people migrating into Europe, the answer is pretty unambiguously “yes.” We have evidence of dramatic, rapid selection for genes that result in lighter skin among these people. Many of the gene variants responsible for lightly pigmented skin in Europeans had been long present among ancient humans living in Africa (as documented by Crawford & colleagues in “Loci Associated with Skin Pigmentation Identified in African Populations”), but then spread rapidly among Europeans approximately 4,000 years ago (as documented by Mathieson & colleagues in “Genome-Wide Patterns of Selection in 230 Ancient Eurasians”).
The dramatic selection for genes associated with lightly pigmented skin in Europe occurred within the span of about a thousand years, and occurred about 30,000 or 40,000 years after Homo sapiens first populated that region.
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Among the various groups of ancient humans who migrated toward similar latitudes, only the indigenous people of Northern Europe evolved lightly pigmented skin. This trait spread rapidly (by evolutionary standards) about 4,000 years ago.
This timing is similar to the spread of lactose tolerance genes among the people of Northern Europe. Most animals, including most humans, can’t digest milk in adulthood. Even among humans who live in cultures where cows’ milk is a major component of the diet, many people can’t digest it and will experience routine gastrointestinal distress and diarrhea. (Which is serious! Although a few bottles of Gatorade would save their lives, diarrhea still kills about 2 million people per year. Among ancient humans, diarrhea could easily cause deaths by malnutrition, dehydration, or increased susceptibility to disease.)
And yet, just before the Europeans’ vast spree of kidnapping, abduction, and resource extraction led to massive amounts of human migration (which began approximately 500 years ago), nearly 95% of the people living in Europe had the genes for lactose tolerance.
That’s a huge change, and really fast! Which should make us realize that something strange might be going on with this group of people – they must’ve had particularly atrocious diets. Which helps explain why they’d need lighter skin.
After all, vitamin D is a dietary nutrient. If you get enough vitamin D from your food, there’s no downside to darkly pigmented skin. And, as David Graeber & David Wengrow describe comically in The Dawn of Everything(“We might call this the ‘all the bad spots are taken!’ argument”), most ancient humans chose to live in places where they could find food, water, and shelter. Otherwise they’d migrate.
Yet, in a savage twist of fate, the same culture that generally resulted in low-quality diets – farming – also made migration more difficult. People stayed near their farms, with their insufficient amounts of low-quality food, because that way they’d at least have something.
I’ve written previously about the social and environmental repercussions of ancient farming – a lovely essay, in my opinion! – but in order to understand the evolution of skin color, all we really need to know is the impact of farming on human health. As James Scott writes in Against the Grain,
“Evidence for the relative restriction and impoverishment of early farmers’ diets comes largely from comparisons of skeletal remains of farmers with those of hunter-gatherers living nearby at the same time. The hunter-gatherers were several inches taller on average. This presumably reflected their more varied and abundant diet. It would be hard, as we have explained, to exaggerate that variety. Not only might it span several food webs – marine, wetland, forest, savanna, arid – each with its seasonal variation, but even when it came to plant foods, the diversity was, by agricultural standards, staggering. The archaeological site of Abu Hureyra, for example, in its hunter-gatherer phase, yielded remains from 192 different plants, of which 142 could be identified, and of which 118 are known to be consumed by contemporary hunter-gatherers.”
The crops and livestock raised by farmers in Northern Europe provide very little vitamin D. But ancient humans often settled in areas where they could catch fish, which provides plenty of dietary vitamin D (as measured by Schmid & colleagues for their study “Natural Vitamin D Content in Animal Products”).
As it happens, if the picture from The Magic School Bus Explores Human Evolution were an accurate depiction of those people’s diet (not to mention their clothes, exposing quite a bit of skin!), they’d probably experience very little selective pressure for lighter skin.
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Whenever we discuss evolution, it’s important to remember that natural selection doesn’t enrich for traits that are “better.” There’s rarely any such thing as “better.” Consider: the ancestors of starfish had brains! But – given their particular environment – their lineage was more successful after evolving to be brainless. Or: the ancestors of penguins could fly! But – given their particular environment – their lineage was more successful after evolving to be flightless.
We humans have long legs and arched feet that are great for running, but these same long legs and stubby toes make us so much worse at climbing trees than a chimpanzee. It’s a trade-off. (And a trade-off that I’m pretty happy with, given that I love to run and am afraid of heights.)
Lightly pigmented skin carries a very clear cost – UV penetration with its attendant folate degradation, skin cancers, and discomfort – and only carries a compensatory benefit at extreme northern or southern latitudes among ancestral populations with diets low in vitamin D.
We do ourselves a major disservice – and perpetuate Eurocentric racism – if we consider the selective pressures encountered by one particular group of Homo sapiens to be the default against which all others are measured.
Like many people, I have a weak grasp on long times. My family often visits a nearby pioneer reenactment village where the buildings and wooden gearworks of its water-powered corn mill are about two hundred years old; I feel awed. In Europe, some buildings are a thousand years old, which sounds incredible to me.
These are such small sips of evolutionary time.
Humans have roamed our world for hundreds of thousands of years. Large dinosaurs ruled our planet for hundreds of millions of years. Animals whom we’d recognize as Tyrannosaurus rex prowled for the final 2.5 million years of that, with their last descendants dying about 66 million years ago.
My mind struggles to comprehend these numbers.
I found myself reflecting on this after a stray remark in Oded Galor’s The Journey of Humanity: The Origins of Wealth and Inequality: “Why is such a powerful brain so rare in nature, despite its apparent advantages?”
Galor’s question seems reasonable from the vantage of the present. We live on a planet where 96% of the mammalian biomass is either our own species or prey animals we’ve raised to eat. The total mass of all surviving wild dinosaurs – otherwise known as “birds” – is less than a thirtieth the mass of humans. We’ve clearly conquered this world. Our dominance is due to our brains.
And this moment – right now! – feels special because we’re living through it. From a geological or evolutionary perspective, though, the present is a time much like any other. If we represent the total lifespan of our sun as a 24-hour day (which is much more sensible than representations with the present moment at the end of the day), the current time would be 10:58 a.m., and our sun will become so hot that it boils away all our planet’s liquid water at 7:26 p.m. Between now and then, though, we have a whole workday’s time for life to continue its beautiful, chaotic evolutionary dance. Perhaps quite soon – maybe just a million years from now, or 10 million, which is less than two minutes of our total day – the descendants of contemporary parrots, crows, or octopuses could become as intelligent as contemporary Homo sapiens.
As a human, I’m biased toward thinking that parrots and crows would have a better chance than octopuses – after all, these birds face a similar evolutionary landscape to my own ancestors. They’re long-lived, social species that invest heavily in childcare, are anatomically well-suited for tool use, and face few risks from predators.
Or rather, parrots would face few risks if humans weren’t around. Unfortunately them, a voracious species of terrestrial ape is commandeering their homeland and kidnaps their young to raise as pets. But crows can thrive in a human-dominated landscape – some crows even use our cars as tools, cracking nuts by placing them in urban crosswalks then retrieving their snack after the light turns red.
Octopuses, however, are short-lived and antisocial. They’re negligent parents. Their brief lives are haunted by nightmarish predators. And yet. Some octopuses are already quite intelligent; their intelligence appears to confer a reproductive advantage (if only by virtue of survival); their bodies are well-suited for tool use. Certain types of tools, like flaked stone, would be more difficult to create underwater, but many octopuses are capable of brief sojourns into open air. So I wouldn’t rule them out. Sometimes evolution surprises us – after all, the world has a lot of time to wait.
Which means that powerful brains like ours might not be rare in the future. Especially if our species does something stupid – like engaging in nuclear war, succumbing to global pandemic, or ruining crop yields with climate change – and the animal kingdom’s future intelligentsia don’t have to compete with 8 billion Homo sapiens for space and resources.
Also, it’s surprisingly difficult to assess whether powerful brains like ours were rare in the past. Intelligent, tool-crafting, fire-wielding, language-using species have gone extinct before – consider the Neanderthal. Our own ancestors nearly went extinct during past episodes of climate change, like after a volcanic eruption 70,000 years ago. And even if some species during the age of dinosaurs had been as intelligent as modern humans, we might not recover much evidence of their brilliance.
Please note that I’m not arguing that Tyrannosaurus rex wove baskets, wielded fire, or built the Egyptian pyramids. For starters, the body morph of T-Rex is ill-suited for tool use (as depicted in Hugh Murphy’s T-Rex Trying comics). But simply as a thought experiment, I find it interesting to imagine what we’d see today if T-Rex had reached the same level of technological and cultural sophistication as humans had from 100,000 to 10,000 years ago.
If T-Rex made art, we wouldn’t find it. The Lascaux paintings persisted for about 20,000 years because they were in a protected cave, but as soon as we found them, our humid exhalations began to destroy them. Millions of years would crush clay figurines, would cause engraved bone to decompose.
If T-Rex crafted tools from wood or plant fibers, we wouldn’t find them. We can tell that ancient humans in the Pacific Northwest of North America caught an annual salmon harvest by analyzing radioactive isotopes, but we’ve never found evidence of the boats or nets these ancient people used. After a few more radioactive half-lives passed – much sooner than a million years – this would have become invisible to us.
If T-Rex crafted tools from stone, we’d find remnants, but they’d be difficult to recognize. Evidence for human tool use often comes in three types – sharp flakes (usually 1-3 inch blades used as knives or spear tips), a hammer (often just a big round stone), and a core (a hunk of good rock that will be hit with the hammer to knock knife-like flakes off its surface). We’re most likely to realize that a particular rock was a human tool if it’s near a human settlement or if it’s made from a type of sediment rare in the location where contemporary archaeologists found it (which is why we think that an ancient primate took particular interest in the Makapansgat pebble).
Still, time is a powerful force. 66,000,000 years can dull the edges of a flake, or produce sharp rocks through mindless geological processes. It’s been difficult for archaeologists studying submerged sites in ancient Beringia – a mere 30,000 years old! – to know for certain whether any particular rock was shaped by human hands or natural forces. Other stone tools used by ancient humans look a lot like regular rocks to me, for example this 7,000-year-old mortar from Australia or these 9,000-year-old obsidian knives from North America. Ten million more years of twisting, compressing, and chipping might deceive even a professional.
And then there’s the rarity of finding anything from that long ago. Several billion T-Rex have tromped across the land, but we’ve only found as much as a single bone from a hundred of them. 99.999996% of all T-Rex vanished without a trace.
From those rare fossils, we do know that T-Rex brains were rather small. But not all neurons are the same. Work from Suzana Herculano-Houzel’s research group has shown that the number of neurons in a brain is a much better proxy for intelligence than the brain’s total size – sometimes a bigger brain is just made from bigger neurons, with no additional processing power. And the brains of our world’s surviving dinosaurs are made quite efficiently – “Birds have primate-like numbers of neurons in the forebrain.” **
We humans are certainly intelligent. And with all the technologies we’ve made in the past 200 years – a mere millisecond of our sun’s twenty-four hour day – our presence will be quite visible to any future archaeologists, even if we were to vanish tomorrow. But we do ourselves no favors by posturing as more exceptional than we are.
Animals much like us could have come and gone; animals much like us could certainly evolve again. Our continued presence here has never been guaranteed.
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** A NOTE ON NEURON COUNTS: many contemporary dinosaurs have brains with approximately 200 million neurons per gram of brain mass, compared to human brains with approximately 50 million neurons per gram of brain mass. A human brain has a much higher total neuron count, at about 80 billion neurons, than dinosaurs like African Gray Parrots or Ravens, which have about 2 billion neurons, but only because our brains are so much more massive. If the brain of a T-Rex had a similar composition to contemporary dinosaurs, it might have twice as many neurons as our own.
Of course, elephant brains also have three times as many neurons as our own — in this case, researchers then compare neuron counts in particular brain regions, finding that elephant brains have about a third as many neurons specifically in the cerebral cortex compared to human brains. For extinct species of dinosaurs, though, we can only measure the total size of the cranial cavity and guess how massive their brains would have been, with no indication of how these brains may have been partitioned into cerebellum, cerebral cortex, etc.
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Header image: a photograph of Sue at Chicago’s Natural History Museum by Evolutionnumber9 on Wikipedia.
The world is complicated. There’s so much information out there, so much to know. And our brains are not made well for knowing much of it.
I can understand numbers like a dozen, a hundred. I can make a guess at the meaning of a thousand. Show me a big gumball machine and ask me to guess how many gumballs are in it, maybe I’ll guess a thousand, a few thousand.
But numbers like a million? A billion? A trillion? These numbers are important, I know. These numbers might be the population of cities, or of planets, or of solar systems. These numbers might be the ages of species or planets. These numbers might be how many stars are in the sky, or how many stars in the sky might harbor life.
These numbers don’t mean much to me.
I don’t think the problem is just my brain. I’m fairly good with numbers, relative to the average human. It’s been years since I’ve sat in a math class, but I can still do basic integrals and derivatives in my head.
Yet I can’t understand those big numbers. They don’t feel like anything to me.
So we make graphs. Charts. We try to represent information in ways that our meager human brains can grasp.
A good chart can be a revelation. Something that seemed senseless before is now made clear.
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An apocalypse is a revelation. The word “apocalypse” means lifting the veil – apo, off; kalyptein, conceal. To whisk away the cover and experience a sudden insight.
An illustration that depicts information well allows numbers to be felt.
Often, though, we illustrate information and we do it poorly.
The scientific method is gorgeous. Through guesswork, repetition, and analysis, we can learn about our world.
But science is never neutral. We impart our values by the questions we choose to ask, by the ways we choose to interpret the world’s ever-oblique answers.
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Geological time is often depicted as a clock. A huge quantity of time, compressed down into a 24-hour day. Often, this is done with the ostensible goal of showing the relative unimportance of humans.
Our planet has been here for a day, and humans appear only during the final two minutes!
Unfortunately, this way of depicting time actually overemphasizes the present. Why, after all, should the present moment in time seem so special that it resides at midnight on our clock?
The present feels special to us because we’re living in it. From a geological perspective, it’s just another moment.
Geologic textbooks invariably point out (almost gleefully) that if the 4.5-billion-year story of the Earth is scaled to a 24-hour day, all of human history would transpire in the last fraction of a second before midnight.
But this is a wrongheaded, and even irresponsible, way to understand our place in Time. For one thing, it suggests a degree of insignificance and disempowerment that not only is psychologically alienating but also allows us to ignore the magnitude of our effects on the planet in that quarter second.
And it denies our deep roots and permanent entanglement with Earth’s history; our specific clan may not have shown up until just before the clock struck 12:00, but our extended family of living organisms has been around since at least 6 a.m.
Finally, the analogy implies, apocalyptically, that there is no future – what happens after midnight?
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Timefulness is a lovely book, but Bjornerud does not present a corrected clock.
And so I lay in bed, thinking. How could these numbers be shown in a way that helped me to understand our moment in time?
I wanted to fix the clock.
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The first midnight is easy – the birth of our sun. A swirling cloud of gas condenses, heating as gravity tugs the molecules into more and more collisions. Nuclear fusion begins.
Gravity tugs molecules inward, nuclear explosions push them outward. When these are balanced, our sun exists. Twelve o’clock.
Two minutes later, our planet is born. Metal and water and dust become a big rock that keeps swirling, turning, as it orbits the sun. It’s warmed, weakly, by light from the sun – our star shone dimly then, but shines brighter and brighter every day.
Our sun earns low interest – 0.9% each hundred million years, hotter, brighter. But wait long enough, and a low interest is enough.
Someday, shortly before it runs out of fuel, our sun will be blinding.
By 12:18 a.m., there is life on Earth. We’ve found fossils that many billions of years old.
And at 7:26 p.m., there will be no more life. Our sun will have become so bright that its blinding light evaporates all the oceans. The water will boil so hot that it will be flung into space. The Earth will be a rocky desert, coated perhaps in thick clouds of noxious gas.
Currently, it’s 10:58 a.m.
The dinosaurs appeared 35 minutes ago. 9.5 minutes ago, all of them died (except the ancestors of our birds).
Humans appeared 1 minute ago.
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So, we have 3.5 billion years remaining – another 8.5 hours on our clock – before we have to migrate to the stars.
Humans certainly can’t persist forever. Empty space is stretching. Eventually, the whole universe will be dark and cold, which each speck of matter impossibly far from every other.
But our kind could endure for a good, long while. Scaled to the 24-hour day representing the lifespan of our sun, we still have another 300 years before the universe goes dark.
So many stories could fit into that span of time.
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It’s 10:58 a.m., and life on Earth has until 7:26 p.m.
Humans crept down from trees, harnessed fire, invented writing, and built rockets all within a single minute. Life moves fast.
Quite likely, life from Earth will reach the stars.
But it needn’t be us.
The dinosaurs were cool. They didn’t make it.
We naked apes are pretty cool, too. I love our cave drawings, art museums, psychedelic street art. Our libraries. But we’ve also made prodigious mounds of trash. We’re pouring plumes of exhaust into the sky as we ship giant flatscreen televisions from place to place.
We burn a lot of fuel for the servers that host our websites.
We humans aren’t the first organisms to risk our own demise by pumping exhaust into the atmosphere. The industrial revolution was fueled by ancient plants – our engines burn old sunlight. But many microbes are happy to eat old sunlight, too. These microbes also pump carbon dioxide into the air. They’ve warmed our planet many times before – each time the permafrost thawed, microbes went to town, eating ancient carbon that had been locked up in the ice.
Foolish microbes. They made the Earth too hot and cooked themselves.
Then again, the microbes may have more modest goals than us humans. We’ve found no fossils suggesting that the microbes tried to build spaceships.
For our endeavors, we’ve benefited from a few thousand years of extremely stable, mild climate.
We still have 8.5 hours left to build some spaceships, but a thirty second hot squall at 10:59 a.m. would doom the entire project.
So much time stretches out in front of us. We could have a great day. We, in continuation of the minute of humans who preceded us, and continued by the seconds or minutes or hours of humans who will be born next.
We shouldn’t let our myopic focus on present growth fuck up the entire day.
Honestly? My children are four and six. I’d be so disappointed if I took them for a hike and they guzzled all their water, devoured all their snacks, within the first minute after we left our house.
In Sue Burke’s Semiosis, humans reach an alien world with intelligent plants.
The settlers find themselves afflicted by inexplicable infertility. Most women are able to bear children, but many men are sterile. The settlement develops a culture in which women continue to marry based on the vagaries of affection, but from time to time, a woman will kiss her spouse goodnight before venturing off for an evening’s energetic tussle with a fertile man.
The human settlement has established itself at the base of a single plant. This plant has ocular patches and can recognize individual humans. The plant provides fruit that seems exquisitely tailored to each person’s nutritional needs. In return, the humans carefully tend the plant – irrigating its groves, clearing away competitors, and fertilizing new growth.
The plant manipulates its human caretakers. By tweaking the composition of their food, it controls the humans’ health. Selectively instilling infertility or fecundity allows the plant to direct human evolution. Among the fourth generation of human settlers, more than half of all children were sired by a placid man who was so contemplative and empathetic that he learned to communicate with the host plant.
The plant domesticated its human caretakers.
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Here on Earth, flowering plants also co-evolved with animals.
Plants could very well consider themselves the dominant species in these relationships – after all, plants use animals to do their bidding. Plants offer tiny drips of nectar to conscript insects to fertilize their flowers. Plants offer small fruits to conscript mammals to spread their seeds. And plants far outlive their servants – thousands of generations of animals might flit by during the lifetime of a single tree.
Some plants directed the evolution of their helpers so well that the species are inextricably linked – some insects feed on only a single species of plant, and the plant might rely on this single species of insect to fertilize its flowers. If either the plant or insect disappeared, the other would go extinct.
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In Semiosis, the alien plant changes its attitude toward humans over the generations. At first it was concerned only with control and utility. The motile beasts were a tool that it could manipulate with pleasing colors and psychoactive fruits.
Eventually, though, the plant develops an affection for its human wards. Of course, these humans are markedly different from the people who first arrived on this planet.
The plant’s affections changed in the same way that our own attitude toward wolves softened as we manipulated the species. Many humans are still reflexively afraid of wolves. We tell children stories about Little Red Riding Hood; when I’m walking in the woods, sometimes I find myself humming the refrain from “Peter and the Wolf.” The ecosystem of Yellowstone Park was devastated when we murdered all the wolves during the 1920s; willow and beaver populations have rebounded since wolves were reintroduced in the 1990s (most likely because wolves mitigate the damage done by uncontrolled elk populations); now that Yellowstone’s wolf population isn’t critically endangered, states surrounding the park are letting human hunters shoot wolves again.
And yet, we giggle at the antics of domesticated dogs.
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Among wild animals, the most aggressive individuals are often the most fecund. Wolves who can fight for and hold the alpha rank get to breed; the others don’t.
During domestication, breeding patterns are altered. To create dogs, we selected for the most docile individuals. If you could expand your temporal horizons wide enough, all populations might seem as mutable as clay. A species flows through time, ever changing, evolving such that the traits that best lead to viable children become more common. In the wild, a speedy rabbit might have the most children, because it might survive for more breeding seasons than others. On a farm, the most docile rabbit might have the most children, because its human handlers might give a docile male more time among the females.
Domestication seems to change animals in stereotyped ways. Zoologist Dmitry Belyayev designed an experiment with wild foxes. Only the foxes that were least fearful of humans were allowed to breed; over the course of some dozen generations, this single criterion resulted in a large number of behavioral and morphological changes. The domesticated foxes produce less adrenaline; they have narrower faces; they have floppier ears. This suite of traits seems to be present in almost all domesticated species.
Cats still have pointy ears. As it happens, cats are barely domesticated.
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Humans seem to be self-domesticated. A few hundred thousand years ago, our ancestors lived in very small groups, maybe one or two dozen individuals. After humans diverged from the last common ancestor that we shared with bonobos and chimpanzees, most human species still lived in groups of about this size. Neanderthals may have lived in groups as small as six.
Eventually, Homo sapiens drove all other human species to extinction. A major competitive advantage was that Homo sapiens lived and worked in groups as large as a hundred. With so many people cooperating, they could hunt much more efficiently. A violent conflict between six Neanderthals and a clan of a hundred Homo sapiens would not go well for the Neanderthals.
In the modern world, the population densities of urban areas force humans to be even more docile than our recent ancestors. But even with our whole evolutionary history promoting cooperation, many people struggle to be calm and kind within the crowded confines of a city. Some can do it; others feel too aggressive.
When a person’s disposition is ill-suited to the strange environment we’ve made, we punish. We shunt people to high school detention, or jail.
In Semiosis, the plant overlord reacts by limiting fertility.
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As in Richard Powers’s Overstory, the perspective of a long-lived, immobile plant would be markedly different from ours. Human generations flit by as a plant continues to grow.
The bamboo forest/grove in Arashiyama, Kyoto, Japan. Photograph by Daniel Walker on Flickr.
Domestication takes generations – in Belyayev’s fox experiment, twenty generations passed before a third of the population was tame – but an intelligent plant could wait. By selecting which individuals get to pass on their genes, huge changes can be made. From wolves, we created Great Danes and Chihuahuas. From a scruffy grass we evoked buxom ears of corn, as though by glacial magic.
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In particularly dark eras of our past, humans have tried to direct our own evolution. Social Darwinists in the United States forcibly sterilized people whom they disliked. Politicians in Nazi Germany copied the legal language of the United States when they sought philosophical justification for the murder of entire religious and ethnic groups.
By putting the motivation inside the mind of a plant, Burke is able to explore the ramifications of directed human evolution without alluding to these evil regimes.
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In jail, somebody said to me, “I heard that humans were evolving to have really long fingers, so we could type real fast, and big-headed hairless bodies.”
“Yeah, yeah,” somebody added, “I saw this thing on the Discovery channel, it was like, you know the way they show all those aliens on the X-Files? That humans were gonna be like that, like the aliens were just us coming back to visit from the future.”
“Humans are definitely still evolving. But evolution doesn’t have a goal. It just selects for whichever properties of a creature are best for making copies of itself.”
“With modern medical care, we don’t die so easily. So the main driver of evolution is the number of kids you have. If you have more kids than I do, then you’re more fit than I am. Future humans will look more like you than me.”
For the moment, let’s set aside the question of why I was reading a review titled “Plants Neither Possess nor Require Consciousness.” Instead, I’d like to share a passage from the end of the article:
Plant
neurobiologists are hardly the first biologists to ascribe consciousness,
feelings, and intentionality to plants.
…
Erasmus
Darwin, [Charles] Darwin’s grandfather and
a believer in free love, was so taken with the Linnaean sexual system of
classification that he wrote an epic poem, The Loves of Plants, in which
he personified stamens and pistils as ‘swains’ and ‘virgins’ cavorting on their
flower beds in various polygamous and polyandrous relationships.
Maybe
you were startled, just now, to learn about the existence of risqué plant
poetry. Do some people log onto
Literotica to read about daffodils or ferns?
But what
caught my attention was Erasmus Darwin’s designation as a believer in free
love.
In a flash, an entire essay composed itself in my mind. Charles Darwin’s grandfather was a polyamorist! Suddenly, the origin of The Origin of the Species made so much more sense! After all, exposure to polyamory could help someone notice evolution by natural selection. An essential component of polyamory is freedom of choice – during the 1800s, when nobody had access to effective birth control, people might wind up having children with any of their partners, not just the one with whom they were bound in a legally-recognized and church-sanctioned marriage.
Evolution occurs because some individuals produce more offspring than others, and then their offspring produce more offspring, and so on. Each lineage is constantly tested by nature – those that are less fit, or less fecund, will dwindle to a smaller and smaller portion of the total population.
Similarly, in relationships where choice is not confined by religious proscription, the partners are under constant selective pressure if they hope to breed. When people have options, they must stay in each other’s good graces. They must practice constant kindness, rather than treating physical affection as their just desserts.
I felt
proud of this analogy. To my mind,
Erasmus Darwin’s belief in free love had striking parallels with his grandson’s
theory.
And it’s such a pleasure when essays basically write themselves. All I’d need to do was skim a few biographies. Maybe collect some spicy quotes from Erasmus himself. And I’d try to think of a clever way to explain evolution to a lay audience. So that my readers could understand why, once I’d learned this juicy tidbit about Erasmus, his connection to Charles Darwin’s theory seemed, in retrospect, so obvious.
My essay
failed.
I wish it hadn’t, obviously. It was going to be so fun to write! I was ready to compose some sultry plant poetry of my own.
And I feel happy every time there’s another chance to explain evolution. Because I live in a part of the United States where so many people deny basic findings from science, I talk about this stuff in casual conversations often. We regularly discuss evolutionary biology during my poetry classes in jail.
But my
essay wasn’t going to work out. Because
the underlying claim – Erasmus Darwin believed in free love! – simply isn’t
true.
Maybe you have lofty ideals about the practice of science. On the children’s record Science Is for Me,Emmy Brockman sings:
That’s the goal. A good scientist considers all the possibilities. It’s hard work, making sure that confirmation bias doesn’t cause you to overlook alternative explanations.
But
scientists are human. Just like anybody
else, we sometimes repeat things we’ve heard without considering whether any
evidence ever justified it.
In The
Human Advantage, neuroscientist Suzana Herculano-Houzel describes how
baffled she felt when she began reading scientific papers about the composition
of our brains.
Although
the literature held many studies on the volume and surface area of the brain of
different species, and various papers on the densities of neurons in the
cerebral cortex, estimates of numbers of neurons were scant. In particular, I could find no original
source to the much-repeated “100 billion neurons in the human brain.”
…
I later
ran into Eric Kandel himself, whose textbook Principles of Neural Science,
a veritable bible in the field, proffered that number, along with the
complement “and 10-50 times more glial cells.”
When I asked Eric where he got those numbers, he blamed it on his
coauthor Tom Jessel, who had been responsible for the chapter in which they
appeared, but I was never able to ask Jessel himself.
…
It was
2004, and no one really knew how many neurons could be found on average in the
human brain.
Unsatisfied
with the oft-repeated numbers, Herculano-Houzel liquified whole brains in order
to actually count the cells. As it
happens, human brains have about 86 billion neurons and an equal number of
glial cells.
Or,
consider the psychology experiments on behavioral priming. When researchers “prime” a subject, they
inoculate a concept into that person’s mind.
The basic idea here is relatively uncontroversial. It’s the principle behind advertising and paid product placement – our brains remember exposure while forgetting context. That’s why political advertisements try to minimize the use of opponents’ names. When people hear or see a candidate’s name often, they’re more likely to vote for that candidate.
Facebook has also demonstrated again and again that minor tweaks to the inputs that your brain receives can alter your behavior. One shade of blue makes you more likely to click a button; there’s a size threshold below which people are unlikely to notice advertisements; the emotional tenor of information you’re exposed to will alter your mood.
When research psychologists use priming, though, they’re interested in more tenuous mental links. Study subjects might be primed with ideas about economic scarcity, then assessed to see how racist they seem.
The first study of this sort tested whether subconsciously thinking about elderlies could make you behave more like an elderly person. The researchers required thirty undergraduate psychology students to look at lists of five words and then use four of these words to construct a simple sentence. For fifteen of these students, the extra word was (loosely) associated with elderly people, like “Florida,” “worried,” “rigid,” or “gullible.” For the other fifteen, the words were deemed unrelated to elderlies, like “thirsty,” “clean,” or “private.”
(Is a stereotypical elderly person more gullible than private? After reading dozens of Mr. Putter and Tabby books — in which the elderly characters live alone — I’d assume that “private” was the priming word if I had to choose between these two.)
After completing this quiz, students were directed toward an elevator. The students were timed while walking down the hallway, and the study’s authors claimed that students who saw the elderly-associated words walked more slowly.
There’s
even a graph!
This conclusion is almost certainly false. The graph is terrible – there are no error bars, and the y axis spans a tiny range in order to make the differences look bigger than they are. Even aside from the visual misrepresentation, the data aren’t real. I believe that a researcher probably did use a stopwatch to time those thirty students and obtain those numbers. Researchers probably also timed many more students whose data weren’t included because they didn’t agree with this result. Selective publication allows you to manipulate data sets in ways that many scientists foolishly believe to be ethical.
If you were to conduct this study again, it’s very unlikely that you’d see this result.
Some scientists are unconcerned that the original result might not be true. After all, who really cares whether subconscious exposure to words vaguely associated with old people can make undergraduates walk slowly?
UCLA psychology professor Matthew Lieberman wrote,
What we
care about is whether priming-induced automatic behavior in general is a real
phenomenon. Does priming a concept
verbally cause us to act as if we embody the concept within ourselves? The answer is a resounding yes. This was a shocking finding when … first discovered … in 1996.
Lieberman bases this conclusion on the fact that “Hundreds of studies followed showing that people primed with a stereotype embodied it themselves.” Continued success with the technique is assumed to validate the initial finding.
Unfortunately, many if not most of those subsequent studies are flawed in the same way as the original. Publication biases and lax journal standards allow you to design studies that prove that certain music unwinds time (whose authors were proving a point) or that future studying will improve your performance on tests today (whose author was apparently sincere).
Twenty years of mistaken belief has given the walking speed study – and its general methodology – an undeserved veneer of truth.
Erasmus
Darwin didn’t believe in free love. But
he did have some “radical” political beliefs that people were unhappy
about. And so, to undermine his
reputation, his enemies claimed that he believed in free love.
Other
people repeated this slander so often that Erasmus Darwin is now blithely
described as a polyamorist in scientific review articles.
So, why
did conservative writers feel the need to slander Erasmus Darwin? What exactly were his “radical” beliefs?
Erasmus Darwin thought that the abject mistreatment of black people was wrong. He seems to have thought it acceptable for black people to be mistreated – nowhere in his writings did he advocate for equality – but he was opposed to the most ruthless forms of torture.
Somewhat. His opposition didn’t run so deep that he’d
deny himself the sugar that was procured through black people’s forced labor.
And,
when Erasmus Darwin sired children out of wedlock – which many upper-class
British men did – he scandalously provided for his children.
In
British society, plenty of people had affairs.
Not because they believed in free love, but because they viewed marriage
as a fundamentally economic transaction and couldn’t get a divorce. But good British men were supposed to keep up
appearances. If a servant’s child
happened to look a great deal like you, you were supposed to feign ignorance.
Even
worse, the illegitimate children that Erasmus Darwin provided for were female. Not only did Darwin allow them to become
educated – which was already pretty bad, because education made women less
malleable spouses – but he also helped them to establish a boarding school for
girls. The contagion of educated women
would spread even further!
This was all too much for Britain’s social conservatives. After all, look at what happened in France. The French were unduly tolerant of liberal beliefs, and then, all of a sudden, there was murderous revolution!
And so Erasmus Darwin had to be stopped. Not that Darwin had done terribly much. He was nationally known because he’d written some (mediocre) poetry. The poetry was described as pornographic. It isn’t. Certain passages anthropomorphize flowers in which there are unequal numbers of pistils and stamens. It’s not very titillating, unless you get all hot and bothered by the thought of forced rhymes, clunky couplets, and grandiloquent diction. For hundreds of pages.
While
reading about Erasmus Darwin, I learned that some people also believe that he
was the actual originator of his grandson’s evolutionary theories. In a stray sentence, Erasmus Darwin did write
that “The final course of this contest between males seems to be, that the
strongest and most active animal should propagate the species which should thus
be improved.” This does sound rather
like evolution by natural selection. But
not quite – that word “improved” hints at his actual beliefs.
Erasmus
Darwin did believe all life had originated only once and that the beautiful
variety of creatures extant today developed over time. But he thought that life changed from simple
to complex out of a teleological impulse.
In his conception, creatures were not becoming better suited to their
environment (which is natural selection), but objectively better (which
isn’t).
I’m not arguing that Charles Darwin had to be some kind of super genius to write The Origin of the Species. But when Charles Darwin described evolution, he included an actual mechanism to rationalize why creatures exist in their current forms. Things that are best able to persist and make copies of themselves eventually become more abundant.
That’s it. Kind of trivial, but there’s a concrete theory backed up by observation.
Erasmus
Darwin’s belief that life continually changed for the better was not unique,
nor did it have much explanatory power.
In the
biography Erasmus Darwin, Patricia Fara writes that,
By the
end of the eighteenth century, the notion of change was no longer in itself
especially scandalous. For several
decades, the word ‘evolution’ had been in use for living beings, and there were
several strands of evidence arguing against a literal interpretation of the
Bible. Giant fossils – such as mammoths
and giant elks – suggested that the world had once been inhabited by distant
relatives, now extinct, of familiar creatures.
Animal
breeders reinforced particular traits to induce changes carried down through
the generations – stalwart bulldogs, athletic greyhounds, ladies’ lapdogs. Geological data was also accumulating:
seashells on mountain peaks, earthquakes, strata lacking fossil remains – and
the most sensible resolution for such puzzles was to stretch out the age of the
Earth and assume that it is constantly altering.
Charles
Darwin thought deeply about why populations of animals changed in the
particular way that they did. Erasmus
Darwin did not. He declaimed “Everything
from shells!” and resumed writing terrible poetry. Like:
IMMORTAL
LOVE! who ere the morn of Time,
On wings
outstretch’d, o’er Chaos hung sublime;
Warm’d
into life the bursting egg of Night,
And gave
young Nature to admiring Light!
*
Erasmus Darwin
didn’t develop the theory of evolution.
You could call him an abolitionist, maybe, but he was a pretty
half-hearted one, if that. By the
standards of his time, he was a feminist.
By our standards, he was not.
He seems
like a nice enough fellow, though. As a
doctor, he treated his patients well.
And he constantly celebrated the achievements of his friends.
Patricia
Fara writes that,
After
several years of immersion in [Erasmus]
Darwin’s writing, I still have a low opinion of his poetic skills. On the other hand, I have come to admire his
passionate commitment to making the world a better place.
And, who
knows? If Erasmus Darwin was alive
today, maybe he would be a polyamorist.
Who’s to say what secret desires lay hidden in a long-dead person’s
soul?
But did Darwin, during his own lifetime, advocate for free love? Nope. He did not. No matter what his political opponents – or our own era’s oblivious scientists – would have you believe.
Header image from the Melbourne Museum. Taken by Ruth Ellison on Flickr.
Every living thing needs
energy. But our world is finite. Energy has to come from somewhere.
Luckily, there’s a lot of potential energy out there in the universe. For instance, mass can be converted into energy. Our sun showers us with energy drawn from the cascade of nuclear explosions that transpire in its core. A tiny difference in mass between merging hydrogen atoms and the resultant helium atom allows our sun to shine.
Our sun radiates about 10^26 joules per second (which is 100,000 times more than the combined yearly energy usage from everyone on Earth), but only a fraction of that reaches our planet. Photons radiate outward from our sun in all directions, so our planet intercepts only a small sliver of the beam. Everything living here is fueled by those photons.
When living things use the sun’s energy, we create order – a tree converts disordered air into rigid trunk, a mouse converts a pile of seeds into more mouse, a human might convert mud and straw into a house. As we create order, we give off heat. Warming the air, we radiate infrared photons. That’s what night vision goggles are designed to see. The net effect is that the Earth absorbs high-energy photons that were traveling in a straight beam outward from the sun … and we convert those photons into a larger number of low-energy photons that fly off every which way.
We the living are chaos machines. We make the universe messier. Indeed, that’s the only way anything can live. According to the Second Law of Thermodynamics, the only processes that are sufficiently probable so as to occur are those that make the world more random.
We’re lucky that the universe started out as such a bland, orderly place – otherwise we might not even be able to tell “before” from “later,” let alone extract enough energy to live.
Dog!
The earliest living things took energy from the sun indirectly – they used heat, and so they were fueled by each photon’s delivery of warmth to the Earth. (Please allow me this little hedge – although it’s true that the earliest life was fueled only by warmth, that warmth might not have come from the sun. Even today, some thermophilic bacteria live in deep sea vents and bask in the energy that leaks from our Earth’s molten core. The earliest life might have lived in similar nooks far from the surface of the Earth. But early life that resided near the surface of the seas seems more likely. Complicated chemical reactions were necessary to form molecules like RNA. Nucleic acids were probably first found in shallow, murky pools pulsed with lightning or ultraviolet radiation.)
Over time, life changed. Organisms create copies of themselves through chemical processes that have imperfect fidelity, after all. Each copy is slightly different than the original. Most differences make an organism worse than its forebears, but, sometimes, through sheer chance, an organism might be better at surviving or at creating new copies of itself.
When that happens, the new
version will become more common.
Over many, many generations, this process can make organisms very different from their forebears. When a genome is copied prior to cell division, sometimes the polymerase will slip up and duplicate a stretch of code. These duplication events are incredibly important for evolution – usually, the instructions for proteins can’t drift too far because any change might eliminate essential functions for that cell. If there’s a second copy, though, the duplicate can mutate and eventually gain some new function.
About two billion years ago, some organisms developed a rudimentary form of photosynthesis. They could turn sunlight into self! The energy from our sun’s photons was used to combine carbon dioxide and water into sugar. And sugar can be used to store energy, and to build new types of structures.
Photosynthesis also releases oxygen as a biproduct. From the perspective of the organisms living then, photosynthesis poisoned the entire atmosphere – a sudden rise in our atmosphere’s oxygen concentration caused many species to go extinct. But we humans never could have come about without all that oxygen.
Perhaps that’s a small consolation, given that major corporations are currently poisoning our atmosphere with carbon dioxide. Huge numbers of species might go extinct – including, possibly, ourselves – but something else would have a chance to live here after we have passed.
In addition to poisoning the atmosphere, photosynthesis introduced a new form of competition. Warmth spreads diffusely – on the early Earth, it was often sheer chance whether one organism would have an advantage over any other. If you can photosynthesize, though, you want to be the highest organism around. If you’re closer to the sun, you get the first chance to nab incoming photons.
That’s the evolutionary pressure that induced plants to evolve. Plants combined sugars into rigid structures so that they could grow upwards. Height helps when your main goal in life is to snatch sunlight.
Nothing can live without
curtailing the chances of other living things.
Whenever a plant absorbs a photon, it reduces the energy available for
other plants growing below.
Plants created the soil by
trapping dirt and dust, and soil lets them store water for later use. But there is only so much desalinated
water. Roots reach outward: “I drink your
milkshake!”, each could exclaim.
For a heterotroph, the
brutality of our world is even more clear.
Our kind – including amoebas, fungi, and all animals – can only survive
by eating others. We are carbon
recyclers. Sugar and protein
refurbishers. We take the molecular
machines made by photosynthesizing organisms … chop them apart … and use the
pieces to create ourselves.
Some heterotrophs are
saprophages – eaters of the dead. But
most survive only by destroying the lives of others.
For the earliest heterotrophs, to eat was to kill. But, why worry? Why, after all, is life special? Each photosynthesizing organism was already churning through our universe’s finite quantity of order in its attempt to grow. They took in material from their environment and rearranged it. So did the heterotrophs – they ingested and rearranged. Like all living things, they consumed order and excreted chaos.
The heterotrophs were
extinguishing life, but life is just a pattern that repeats itself. A living thing is a metabolic machine that
self-copies. From a thermodynamic
perspective, only the energetics of the process distinguish life from a
crystal. Both are patterns that grow,
but when a crystal grows, it makes matter more stable than its environment –
life makes matter less stable as it’s incorporated into the pattern.
Your ability to read this
essay is a legacy of the heterotrophs’ more violent descendants. The earliest multicellular heterotrophs were
filter feeders – they passively consumed whatever came near.
But then, between 500 and 600 million years ago, animals began to hunt and kill. They would actively seek life to extinguish. To do this, they needed to think – neurons first arose among these hunters.
Not coincidentally, this is also the time that animals first developed hard shells, sharp spines, armored plates – defenses to stop others from eating them.
The rigid molecules that allow plants to grow tall, like cellulose, are hard to digest. So the earliest hunters probably began by killing other animals.
With every meal, you join
the long legacy of animals that survived only by extinguishing the lives of
others. With every thought, you
draw upon the legacy of our forebear’s ruthless hunt.
Even if you’re vegan, your meals kill. Like us, plants have goals. It’s a matter of controversy whether they can perceive – perhaps they don’t know that they have goals – but plants will constantly strive to grow, to collect sunlight and water while they can, and many will actively resist being eaten.
But it makes no sense to value the world if you don’t value yourself. Maybe you feel sad that you can’t photosynthesize … maybe you’d search out a patch of barren, rocky ground so that you’d absorb only photons that would otherwise be “wasted” … but, in this lifetime, you have to eat. Otherwise you’d die. And I personally think that any moral philosophy that advocates suicide is untenable. That’s a major flaw with utilitarianism – rigid devotion to the idea of maximizing happiness for all would suggest that you, as another organism that’s taking up space, constantly killing, and sapping our universe’s limited supply of order, simply shouldn’t be here.
At its illogical extreme, utilitarianism suggests that either you conquer the world (if you’re the best at feeling happy) or kill yourself (if you’re not).
We humans are descended from carnivores. Our ancestors were able to maintain such large brains only by cooking and eating meat. Our bodies lack an herbivore’s compliment of enzymes that would allow us to convert grass and leaves into the full compliment of proteins that we need.
And we owe the very existence of our brains to the hunts carried out by even more ancient ancestors. If they hadn’t killed, we couldn’t think.
Just because we were blessed by a legacy of violence, though, doesn’t mean we have to perpetuate that violence. We can benefit from past harms and resolve to harm less in the present and future.
Writing was first developed by professional scribes. Scientific progress was the province of wealthy artisans. None of the progress of our culture would have been possible if huge numbers of people weren’t oppressed – food that those people grew was taken from them and distributed by kings to a small number of privileged scribes, artisans, philosophers, and layabouts.
When humans lived as hunters and gatherers, their societies were generally equitable. People might die young from bacterial infections, dehydration, or starvation, but their lives were probably much better than the lives of the earliest farmers. After we discovered agriculture, our diets became less varied and our lives less interesting. Plus, it’s easier to oppress a land-bound farmer than a nomadic hunter. Stationary people paid tribute to self-appointed kings.
This misery befell the vast majority of our world’s population, and persisted for thousands of years. But the world we have now couldn’t have come about any other way. It’s horrific, but, for humans to reach our current technologies, we needed oppression. Food was taken from those who toiled and given to those who hadn’t.
Mostly those others
created nothing of value … but some of them made writing, and mathematics, and
rocket ships.
Although the development
of writing required oppression, it’s wrong to oppress people now. It was wrong then, too … but we can’t go back
and fix things.
Although the origin of
your brain required violence, I likewise think we ought to minimize the
violence we enact today. We can’t help
all the animals who were hurt in the long journey that made our world the place
it is now. And we can’t stop killing –
there’s no other way for heterotrophs like us to live.
To be vegan, though, is to reckon with those costs. To feel a sense of wonder at all the world pays for us to be here. And, in gratitude, to refrain from asking that it pay more than we need.
Among worms, there is equality. When worms entwine, each could become a
mother, a father, or both. Neither worm
has grounds to bemoan the fundamental unfairness of our universe – not while
fooling around, at least.
Later, the worms might drown, or be eaten by birds, or be mutilated and held captive by a mole. That all must feel horrible. But while mating, each worm should feel as though it’s been given a fair deal.
Among emperor penguins, both parents
make huge sacrifices for their young.
Each parent will huddle over the egg for months without food, staving
off the Antarctic chill. When it’s time
to trade places, the parents must pass the egg using only their webbed feet –
if they make even a small mistake, the egg will roll away and freeze, killing
the chick inside.
Because each parent puts forth such a
huge amount of effort to raise a chick, each must feel quite choosy during the
mating season. When a pair of penguins
flirt, neither seems to have the upper hand.
Most animals’ reproduction is more
asymmetric. For them – for us –
differing roles can feel unfair.
Often, one partner gets to be pickier
than the other.
Among smooth guardian frogs, fathers are deeply invested in raising their young; mothers hop away after mating, providing no help. Female smooth guardian frogs seem as though they’d be perfectly happy to make babies with anyone. They can always have another fling while a past paramour is protecting the last batch of eggs.
For a male, mating is a serious commitment. He’ll carefully consider his options. And so each female sings to woo him. A common strategy: knowing that males are choosier when it comes to sex, she’ll sing her heart out, hoping to sway his decision.
Among many other species of frogs, males’ songs serve the same purpose. Hoping to woo womenfolk, male bowerbirds build.
Female ducks raise their young. They have the freedom to choose their
mates. Male ducks would have more
leverage during courtship if they planned to contribute as parents. But they don’t.
Male ducks are the natural world’s equivalent of violent incels. Aggrieved by their lack of choice, they rape. This has been going on so long that female ducks’ anatomy has evolved – they can trap unwanted sperm with labyrinth passageways inside their bodies, and are able to straighten the path to fertilization during consensual sex – allowing them to maintain mate choice despite the constant threat of assault.
From an evolutionary perspective,
animals that put forth an effort as parents have earned their
choices. They generally get to indulge
their desires … and, even more importantly, should be safe from those whom they
do not desire.
Among many species, we can see evidence
of this push and pull between devoted parents and the absentees who loudly
sing, “Choose me! Choose me!”
For instance, we can learn a lot about the sex lives of our closest relatives by comparing the males’ genitalia. No, not your uncle – that’d be weird. I mean the great apes. A traditional comparison of gorillas, chimpanzees, and humans is shown below.
Male gorillas claim a territory, and
then the dominant male within each territory feels reasonably certain that
every female living there will mate with him and only him. Although he makes minimal contributions
toward parenting – which means the females should feel free to shop
around for sexual partners – he sways their decision through physical
violence. Mostly he’ll direct aggression
at other males, hoping to stave off their competition, but he’s occasionally
rough with “his” females as well.
For male gorillas to control female sexuality without helping as parents, they had to become huge. As it happens, this evolutionary pressure caused their brains to shrink. They have almost 90% fewer neurons than we’d expect for a primate of that size. If gorillas were egalitarian, they would’ve been more intelligent than humans. But there simply weren’t enough calories for gorillas to have large brains and sufficient brawn to indulge in violent sexual coercion.
There’s less difference in size between
male and female chimpanzees, but male chimpanzees also use violence to sway
mate choice. A male chimpanzee might
attack and kill a mother’s babies in order to impregnate her … but he won’t if
he thinks that they might be his own children.
The safest plan for a mother, then, is
to distribute her sexual favors widely.
Her children will safe from everyone with whom she shared a
dalliance. Maybe she’d like to be choosier,
but each male will only last a few seconds, so the cost must not seem like too
much to bear.
From an evolutionary perspective, then,
male chimpanzees are not competing to be the most beautiful. Nor to be the greatest artists. They don’t sing. They do battle, but they tend to
battle in cooperative gangs, with the outcome being that each male among the
upper echelon will have the chance to get it on. A friendless, low-ranking male might be
chased off every time he attempts to mate, but many others will have an
occasional opportunity.
That’s why male chimpanzees produce so
much sperm. The chance to fertilize a
mother’s egg comes down to probability.
If a chimp ejaculates prodigiously, he’s more likely to sire offspring.
Several human cultures believed that babies are formed from sperm, and that mothers required repeated infusions during pregnancy in order for the child to form correctly. Among the Bari of Venezuela, each man who contributed sperm was treated as a biological father – the child was presumed to inherit virtues from each.
Under these beliefs, polyamory was the best strategy for raising a capable child. A mother needed to consider which qualities would help her children most in life, then spend time astride the men who possessed each. The best singer, the most nimble climber, the most astute tracker – each trait was an evening’s lay away.
And her strategy surely worked. Fooling around with the best singer would probably lead to singing lessons. If the best hunter also shared an orgasm with this child’s mother, he’d make an effort to explain the sights and sounds and rhythms of the forest. Honestly, it makes no difference whether talents come from nature or nurture if fathers are willing to teach every child that their sperm might’ve helped create.
The Bari culture, like that of most other human hunter gatherers, was quite egalitarian compared to our own. But even among hunter gatherers, human fathers were typically shabbier parents than mothers. For instance, fathers who hunted typically claimed to be the ones feeding their families, even in places where the “women’s work” of gathering fruits, nuts and seeds provided more nutrition than meat. But an occasional dead deer confers more bragging rights than a sackful of nuts each day, and human males have long loved to brag.
As humans began to practice agriculture, our societies became less equitable. More and more of the childrearing was done by women.
According to the basic principles of
evolution, this means that women should have had more and more leverage during
courtship. More and more control over
their sexuality. In cultures where
mothers do basically everything – feeding the family, teaching children,
cuddling them through the night – women should have had close to free reign in
choosing their partners.
And there’s biological evidence that human women used to be in control. For instance, many women’s sexual preferences seem to cycle rhythmically. Relatively effeminate, helpful partners are favored most of the time, but ultra-masculine brutes suddenly seem sexy during temporary bursts of hormones. In the past, human women probably made out with multiple different men each year.
That’s why human males – unlike gorillas or chimpanzees – have a strong incentive to provide a rollicking good time in bed. Or in the back of a cave, on the forest floor, alongside the riverbank, wherever. Although there’s been intense debate about the degree of correlation between male penis size and female sexual pleasure, most people seem willing to admit that there’s a link.
When women buy sex toys … well, usually they buy external vibrators. These don’t always resemble the genitalia of any biological organism. Many are designed to look like lipstick tubes or other innocuous objects, for modesty’s sake.
But toys that are designed for penetration? These tend to be much longer and thicker than either a gorilla’s inch-long erection or a chimpanzee’s three-inch, slender shaft. Human males tend to be well endowed because it’s a way to sway women’s choices. By giving her a good time, a man might have the chance to fool around again.
But in addition to huge cocks (relative to other primates – as Jeffrey Yang wrote in his poetry collection An Aquarium: The barnacle has the longest penis / of any animal in proportion / to its body size. Happiness / and proportion: / never be ashamed of evolution), humans also have huge brains. Instead of evolving better and better ways to deliver consensual pleasure, human males invented stories to subvert female mate choice.
Human
males aren’t as horrible as ducks, but we’re close.
Around
the world, human males have used religion as a tool to constrain female
choice. We teach that the natural
inclination toward polyamory is evil. A
woman needs to devote herself to one man.
In many cultures, women are not even allowed to choose who that man will
be.
Even in contemporary experiments on U.S. college students, the presence of sexual competitors leads people to espouse more strident religious beliefs. If you can’t win with your looks, or with your charming personality, why not tell her that it’d be immoral to make eyes at that other guy?
Human
men could have made art like bowerbirds.
We could’ve sung like frogs.
Hell, we could’ve capitalized on the promise of our large genitalia to
deliver such sweating shaking shuddering good fun that our sexual partners
would remain dazzled forever.
If emperor penguins learned about our sex lives, they’d be appalled. “Dude,” a penguin father might say, “you don’t need to coerce her with a sky ghost! Just be a good parent. Then you’ll get to choose, too.”
That’s sound advice, Mr. Penguin. I am trying to be a good parent. Even when the kids are fussing, I try.
Our criminal justice system ensnares people from all walks of life. Occasionally we’ll hear about the arrest of a wealthy sociopath with a penchant for child abuse, like Jared Fogel or Jeffrey Epstein.
But, let’s face it. Justice in this country isn’t applied fairly. If you’re wealthy, your behavior has to be a lot more egregious for you to reap the same punishments as a poor person. If you look white, your behavior has to a lot more egregious for you to reap the same punishments as a black person.
There’s abundant statistical evidence to back up these claims. But the Supreme Court won’t allow any particular individual to petition for reduced punishment based on the statistical evidence. After all, prosecutors, judges, and juries ostensibly came to their decisions based on the unique details of each individual case. Just because people who resemble you are often treated unfairly doesn’t mean that you were treated unfairly, too.
Because we apply punishment so inequitably, our jails and prisons are full of people who’ve been treated poorly by the world. Compared to the average citizen, people in prison grew up with less money, received less education, experienced more trauma. And, no matter what people’s earlier lives were like, if they’re in prison, they’re not being treated well now.
So they have a lot of justifiable grievances against the dominant political, cultural, and religious beliefs of our country. Punished unfairly by their fellow Christians, people sour on Christianity. Inside walls where the demographics make it blatantly obvious that our laws are enforced in a malignantly racist way, racial tensions boil.
At Pages to Prisoners, an organization that sends free books to people inside, we get requests for stuff about Norse mythology, Odinism, and Asatru. Lots of folks ask for material to learn foreign languages – people want to feel like they’ve accomplished something during their time in prison – but I always feel skeptical when somebody wants help learning Icelandic.
Not that there’s anything wrong with Icelandic. And Norse mythology is cool! Unfortunately, a gaggle of violent white supremacists decided that Norse mythology should be the basis for their religion. Starting in the 1970s, a right-wing racist from Florida began sending “Odinist” publications into prisons.
During the thirteenth century, Christian scholars transcribed many of the old Norse myths so that they could better understand the literary allusions of old Icelandic poetry. But they didn’t record anything about ancient religious practice. We barely have any information about most ancient pagan beliefs. Anyone who wants to adopt a pre-Christian European religion now – whether it’s Wicca, Druidism, Odinism, or Celtic polytheism – is basically forced to make things up.
I have nothing against religious invention. All religions were made by human beings – there’s no a priori reason why a religion created long ago, by people who understood much less about the world than we do now, would be better than something you invent today. Sure, ancient religions have been tested by time, suggesting that they possess virtues that their practitioners found helpful over the years, but most ancient religions have their problems, too. Inaccurate cosmologies, scattered hateful passages in their texts, that sort of thing.
So I like the idea of neo-paganism. You want to find a clearing in the woods and
do some moonlit dancing? You’d rather
worship a feminine generative force than a norm-enforcing patriarchal deity? You want to exalt nature as a hearth to be
protected rather than a resource to be exploited? Go right ahead! All of that sounds pretty great to me.
Unfortunately,
neo-paganism as it’s currently practiced in prison tends to be pretty hateful.
That’s why I’ve been
working on a set of anti-racist pamphlets about Norse mythology. Currently, when people ask for The Poetic
Edda or whatever, we send a friendly letter saying that we don’t have it,
and also that we generally don’t stock that sort of thing because it runs afoul
of our anti-hate policy.
But the Norse myths are
certainly no more hateful than Biblical myths, and we send plenty of
those. The main difference is that
centuries of continued Christian practice have created a scaffolding of gentler
beliefs around the stories in the Bible.
The text of Psalm 137
states that “Happy shall he be, that taketh and dasheth thy little
ones against the stones.” But the
text is a tool, not the entirety of the religion. The practice of Christianity frowns upon
the murder of any human infant. Whether
you like the kid’s parents or not.
We’d be better off if Pages to Prisoners could send warm-hearted material about Norse mythology to people. Sure, you can interpret the Norse myths as endorsing a war-mongering death cult. You can interpret the Old Testament that way, too. But you can also interpret the Norse myths as environmentalist. Feminist. Supporting the pursuit of knowledge. Judging strangers based upon their merits, not their appearance.
Because contemporary
Odinism is so entangled with white supremacy, though, our pamphlet will have to
address skin color and genetic heritage directly. It’s a fraught topic. Lots of people in the U.S. don’t like any discussion
of evolution. Some people feel squigged
out when they learn that contemporary birds evolved from the same set of common
ancestors as the dinosaurs. And that’s far
less emotionally charged than a description of human evolution.
Plus, skin color still has huge implications for how people are treated in the United States. Consider, um, those prison demographics I cited above. And so discussions about the evolution of epidermal melanin concentrations are especially tense. Although the underlying biology is simple – some places have more sunlight than others! – because people think it matters, it does.
I’ve found that these conversations are actually a decent way to get people interested in the study of archeology and biology, though. After we’ve discussed this in jail, people have asked me to bring research papers and textbooks so that they could learn more.
Whenever two groups of an organism stop mating with each other, they’ll slowly drift apart. This rift might occur because the groups became physically separated from each other. Maybe one group migrated to an island. In contemporary times, maybe the groups were separated when humans built a new highway bisecting a habitat. Maybe two sets of similar-looking insects mate apart because they’re eating fruits that ripen at different times.
Or the groups might stop mating with each other because a chance mutation caused members of one group to want their sexual partners to smell a certain way. Various species of stickleback are able to interbreed – they identify other members of their kind based on smell. But water pollution has overwhelmed the fishes’s senses, leading the fish to mate indiscriminately.
If humans hadn’t
polluted their waters, though, these sticklebacks would have drifted farther
and farther apart until it became impossible for them to interbreed. No matter how many sense-suppressing
chemicals we dumped.
We don’t know what caused the initial rift between our ancestors and the ancestors of contemporary chimpanzees. About 4 million years ago, though, these groups stopped having children together. By 2 millions years ago (at least 100,000 generations later), these groups looked quite different from each other. Although it’s possible that these organisms could have still mated with each other and raised viable progeny, they rarely did.
One group of these
creatures, which included our ancestors, had a tucked pelvis and mostly upright
posture. This allowed for a good vantage
while scavenging and, eventually, hunting.
The other group, which includes chimpanzees’ ancestors, mostly moved on
all fours. This body plan results in
fewer mothers dying during childbirth.
As ever, there are trade-offs to be made.
Up until about 2 million
years ago, all our ancestors lived in Africa.
But then they began to migrate.
Over the next million years, they explored much of the globe. By about 500,000 years ago, half a dozen
different types of humans lived in Africa, Europe, and Asia. The difference between one population to the
next was not like the racial differences among contemporary humans, but more
like the difference between lions and tigers, or between polar bears and brown
bears. Scientists describe them as
distinct species. Although they were
similar enough that they could have sex and raise children together, they
rarely did – they lived in distinct parts of the world and had begun to evolve
adaptations to their specific environments.
Evolution isn’t easy. Nor is it quick. Just because a certain trait would be
advantageous doesn’t mean that creatures will acquire it. In the desert, it would help to have
adaptations for water retention like camels, or long ears like jackrabbits to
cool the blood. But a trait can only
spread after a random mutation creates it.
And, even if a trait is very helpful, if only one individual is born
with the adaptation, there’s no guarantee that it will have enough children for
the benefit to spread through the population.
Once a beneficial trait has a good toe-hold – present in perhaps 1% to 10% of the population – then we can expect it to flourish. But below that amount, even great adaptations might die off due to bad luck. That’s why it takes so many generations – tens of thousands, or hundreds of thousands – before you see organisms become drastically better suited for the environment. Even when scientists do directed evolution experiments in the lab, it takes about this many generations for a population of bacteria to evolve ways to consume a new food source, for instance.
By 500,000 years ago, the various species of humans were recognizably different. Denisovans lived in the mountains, and their hemoglobin genes allowed them to avoid altitude sickness. Their blood was less likely to clot and cause strokes, and they could extract more oxygen from the thin air. These are incredibly beneficial traits. Even though the Denisovans went extinct about 40,000 years ago, about 40% of people currently living in Tibet have copies of the Denisovan hemoglobin gene.
Our ancestors migrated east to the Denisovans’ homeland just before the Denisovans went extinct. To be perfectly honest, we probably killed them. But before or during this genocide, a few of our ancestors must have had sex with the locals. And then the bi-racial children of these Homo sapiens / Denisovan couplings must have been significantly better off for the gene to spread so widely.
The Neanderthal lived at
high latitude. Over many generations,
their average skin color became paler.
In part, this was probably due to the lack of selective pressure. Think about a dodo – there was no advantage
for these birds to lose their fear of humans.
But, because the dodos were living on an island that no humans traveled
to, there was also no harm in the birds becoming fearless.
Dodos lost a beneficial
trait – fear – because their fear wasn’t actively needed. It’s kind of like the airbags in an old
car. If your car’s engine goes bad,
you’ll notice right away. Turn the key,
hear it sputter. You use the engine
every time you drive. But your airbags
could get worse without you noticing … and then, in the moment when they’re
needed, they won’t deploy.
Humans living near the equator need epidermal melanin. If you don’t have enough melanin, you’ll get sunburns, which exacerbate the risk of infection and dehydration; you’ll suffer radiation-induced DNA damage, which leads to skin cancer; and you’ll lose folate, which means that pregnant women will have more birth defects.
The most recent ancestors
that humans and chimpanzees shared in common had pale skin. Contemporary chimpanzees are still pale. They can afford to be – their fur protects
them from the sun. But our ancestors
lost their fur, probably so that they didn’t overheat while running, and this
led to the evolution of dark skin.
High concentrations of
epidermal melanin distinguished humans from the other apes.
As humans migrated to
higher latitudes, though, they gradually lost this indicator of their
humanity. Because the sunlight was less
intense, there was less selective pressure.
Humans could lose their epidermal melanin in the same way that dodos
lost their fear – not because it was helpful to go without it, but because the
trait went untested in their day to day lives.
They had no way to “realize” how important it was.
Your airbags aren’t
helpful until you crash. And then
they’ll either deploy and save you, or they won’t.
Now, it’s possible that the Neanderthal also experienced some positive selective pressure on their skin color as they migrated north. Over thousands of generations, the Neanderthals may have benefited from paler skin because it increased their production of vitamin D. We don’t know for certain that the Neanderthal felt any evolutionary pressure to have more vitamin D – after all, contemporary Inuit people live at very high latitudes but still have a lot of epidermal melanin – but it’s true that vitamin D deficiency is a big risk among people with crummy diets.
In the past, hunter / gatherers typically ate much healthier, more varied diets than farmers. When humans began to farm, they would mostly eat the one type of plant that they cultivated, rather than the wide mix of plants that could be found growing wild. And when Homo sapiens farmers migrated to northern Europe, their diets were so poor that they even developed loss-of-function mutations in a cholesterol synthesis gene, probably so that they’d have higher concentrations of vitamin D precursors. Among these people, pale skin was probably a big advantage. They’d be ready for the cloudless days when their homeland’s feeble sunlight was enough to make some vitamin D.
Pieter Bruegel the Elder’s The Harvesters.
Around 40,000 years ago,
our planet’s most recent ice age ended.
The world began to warm, and glaciers retreated from Europe. By then, a group of humans living in Africa
were recognizably Homo sapiens.
These were our ancestors. Every
human alive today – no matter what you look like or where your family is from –
is descended from this group of people from Africa. They lived in tribes of twenty to a hundred
people, had darkly pigmented skin, made art, and spoke complex languages.
As the world warmed, some
of these Homo sapiens began to migrate.
These journeys occurred over many generations. Some tribes stayed in Africa; some tribes
ventured north into Europe; others moved east toward Asia. As they traveled, they encountered the humans
who already lived in those places. As
I’ve mentioned, the newcomers occasionally had sex and raised children with the
natives. They probably also killed a lot
of them. Unfortunately, we Homo
sapiens don’t have the best reputation for treating strangers well.
Interbreeding happened
rarely enough that most people living today have about 99% Homo sapiens DNA. Some people, especially if their families are
from Africa, have essentially 100% Homo sapiens DNA. At other extreme, even people whose families
are from Europe have 96% or more Homo sapiens DNA.
Among people living in
Tibet, the Denisovan hemoglobin gene is common, but most other Denisovan genes
are gone.
Like the Neanderthal
before them, the Homo sapiens who ventured north into Europe began to
lose their epidermal melanin. People who
hunted and fished probably became paler simply because there was less risk of
sun damage. Remember, this didn’t happen
all at once. Average skin color would
change only over the course of hundreds or even thousands of generations, not
during the course of a single journeying Homo sapiens’s lifetime.
Our ancestors spent almost
all their time outdoors, which is why even dark-skinned people could probably
synthesize plenty of vitamin D. Among
contemporary humans, vitamin D deficiency is such a big problem because we
spend too much time inside. As I type
this, I’m sitting at a table in the YMCA snack room, lit up by flickering
fluorescent bulbs. This low-quality
light won’t help me make vitamin D.
Instead, I take a daily
supplement. But that doesn’t come near
matching the health and psychological benefits of time outdoors.
Perhaps it’s worth mentioning that people in jail – places not known for providing a rich, high-quality, varied diet – typically get to go outside no more often than once a week. At our local jail, their hour of “outdoor rec” occurs in a little courtyard at the top of the jail, a cement space covered with a chain-linked fence. Outdoor rec often happened at night – a friend who was recently released told me that “This was still nice. You could see some stars. And there’s that restaurant, Little Zagrib, down the street? Sometimes we’d smell foods from their kitchen.”
Treating people that way
is unlikely to help them get better.
But back to our migrants! Descendants of these pale-skinned Homo sapiens continued to explore new territories. Some reached North America about 12,000 years ago, and some of their descendants continued farther, all the way to South America.
As people traveled –
journeys that lasted many generations – they continued to evolve. Indeed, skin color was a trait that came
repeatedly under selective pressure. As
people migrated south into the Americas, they were living progressively closer
and closer to the equator. Compared to
their grandparents, they were bombarded by more intense sunlight. They needed more epidermal melanin.
This is a process that
takes a long time. A family might have
six kids; maybe the two palest kids get sunburned, which makes it more likely
that they’ll develop skin infections and die before they have children of their
own. If this happens again and again,
among many different families, then eventually the whole population will wind
up with slightly darker skin.
A prediction for the distribution of human skin colors based on the intensity of ultraviolet light present at each latitude. Figure from Nina Jablonski & George Chaplin, “The Evolution of Human Skin Color,” in Journal of Human Evolution, 2000.
This figure depicts the (limited) data we have on the distribution of human skin colors before the modern era’s horrific set of forced migrations. In this image, white-colored regions indicate an absence of data, not low concentrations of epidermal melanin among a region’s prehistoric population. Figure from Nina Jablonski & George Chaplin, “The Evolution of Human Skin Color,” in Journal of Human Evolution, 2000.
Because human skin color
has changed during each of the many prehistoric migrations, it isn’t correlated
with other traits. As we entered the
modern era, people’s skin color was lighter or darker based on how close to the
equator their recent ancestors lived.
But human populations migrated so often that there were many different
groups, each with unique cultural and genetic heritages, living at every
latitude. Because skin color is so
closely linked to latitude, this means many different groups shared similar
concentrations of epidermal melanin. And
there’s no evolutionary pressure linking a trait that protects skin to brain
size or intelligence.
As it happens, there are
major events known to have caused a decrease in human brain size (and probably
intelligence). After all, human brains
are costly. Even though there’s a
benefit to being clever, there’s also been constant evolutionary pressure against
large brains.
Large brains kill
mothers. Because humans walk upright,
childbirth is riskier for human mothers than for other primates. Our posture constrains the width of our hips
– both male and female – but a baby’s whole head has to pass through that
narrow passageway.
Having children is so
risky that we evolved to give birth about 3 months prematurely. Human gestation takes about a year, but most
mothers give birth after only 9 months.
This allows a baby’s head to continue to grow outside the mother’s body,
but human babies are totally helpless at birth.
We have to be very devoted parents to keep them alive.
Also, our brains require a
lot of fuel. Human evolution occurred
over such a long, long time that our ancestors lived through many droughts and
calamities. During the hard years, our
ancestors would struggle to get enough to eat, and a large brain makes that
struggle harder.
A person with a smaller
brain requires fewer calories, making that person less likely to starve in lean
times. And, again, it’s worth
remembering that evolution happens over so many generations, among so many
families, that even small changes can add up.
If mothers who have small-headed children can survive a dozen
pregnancies, but mothers with large-headed children die after only a few, then
the trend will be to have people with smaller brains. Intelligence has to be extremely
beneficial to overcome this sort of evolutionary pressure.
Similarly, if people with
small brains are more likely to survive and raise children during droughts,
then, after hundreds of generations of people who have survived dozens of
extended droughts, you’d expect to see more people with small brains.
Many of us have the bad
habit of reflexively thinking about evolution as the gradual development of
more and more complexity. But that’s not
what it is. Evolution is the process by
which things that are better suited for their environment become more
abundant. If the environment is a hard
place to live in, then evolution tends to push for more and more simplicity. When it’s hard to get enough calories, why
waste calories on anything that you don’t really need?
Starfish are descended
from organisms that had brains. But
starfish are brainless. The ancestral
starfish that weren’t wasting energy thinking were more likely to survive.
Which should make you feel
pretty good about your own brain, actually.
Your ability to think is so fabulous that your ancestors evolved larger
and larger brains … even though these brains were sometimes causing us to
starve to death, or kill our mothers.
That’s a valuable thing
you’ve got inside your skull. It cost
our ancestors so much for you to be able to have it.
But, right. Because the cost was so high, human brains did shrink sometimes. Like when we first domesticated dogs. Our ancestors began living with dogs about 30,000 years ago. Dogs were willing to do some thinking for us – they’d sniff out prey and listen for predators at night. Based on the behavior of my family’s dogs, I bet that they licked the faces of screaming children. Maybe that doesn’t seem essential for survival, but I certainly appreciate every time our dogs calm the kids down.
Because we could slough
off a few mental tasks – I don’t need to be so observant if the dog will
help me hunt – our brains could shrink, making childbirth less deadly and
reducing the caloric cost of maintaining our minds each day.
When humans switched from hunting and gathering to agriculture, our brains shrunk further. A hunter / gatherer has to know so much about every plant and animal living nearby; the work asks more of a person’s brain than farming. This evolutionary trend was exacerbated by the fact that people’s diets became way worse when they began to farm. Instead of getting nutrition from a wide variety of different plants and animals, a farmer might eat meals consisting mostly of a single type of grain.
There’s nothing we can do now about these evolutionary trends. Dogs and farming swayed our ancestors’ evolution toward smaller brains, but it’s not as though you can get those neurons back by deciding to take up hunting, or never living with a pet.
But, honestly, our brains are so plastic that our genetic heritage matters less than how we choose to spend our time. By nature, neither gorillas nor parrots will speak human language. But individuals from both these species have been able to learn to communicate with us after we taught them.
Nobody is born with an
innate understanding of mythology, religion, science, or mathematics. None of that can be encoded in your
genes. If you want to understand this
stuff, you’ll have to make an effort to learn it.
Neuron count only suggests
a brain’s potential. You could do
incredible things with a low number – consider, by ways of analogy, the feats
that 1960s NASA accomplished using computers much smaller than a contemporary
telephone. And, conversely, sensory
deprivation will make it much harder to get things done, no matter what your
innate potential.
That’s why I volunteer with Pages to Prisoners. Our brains are capable of wonders. At any age, we can learn and grow. And yet, we lock people into prisons that seem designed to make them worse.
In fantasy novels, trees walk upon their roots and battle with their limbs. That makes sense to me. If I think about two trees interacting, I consider the branches; the taller tree shades the other, limiting its competitor’s growth.
But my perspective is upside down. Trees are standing on the sky, reaching for one another through the earth. They listen underground. They communicate down there, passing messages to one another, or even meals.
Perhaps
their branches grope for sunlight in the unconscious way that my kids’s feet
seek warmth like homing missiles while they sleep. I try to roll over only to find somebody’s
toes wedged under my back.
Year by
year, trees inch their feet toward the sun.
And their engaging social lives are hidden from me, buried
underground. My reflexive perspective gives
me an inverted image of a tree’s world.
I’m surely
not alone in this misunderstanding.
We humans
hold our heads high as we walk across the ground. A major source of tension in human evolution
was arranging our skeletons in such a way that we could walk upright without
too many women dying in childbirth – our posture constrains the shape of the
pelvis.
Although some species do exhibit dramatically different body morphs between males and females, it’s more common for evolutionary changes in one sex to diffusely alter the other. Club-winged manakins have bones that are more dense than other birds, which makes them worse at flying. All club-winged manakins fly poorly, male and female, even though only the males use their dense bones to produce mate-luring music. Or consider the orgasms and nipples of Homo sapiens, which fulfill important biological purposes in one sex, and serve as a vestigial source of fun for the other.
In
prehistoric times, men and women probably hunted together. The evidence is especially compelling for
human populations like the Neanderthal in southern Europe, who lived in such
small groups that they would be unable to kill large prey without help from everyone
in the group. But even if prehistoric
men had hunted alone, their upright stance and endurance running would have
introduced an evolutionary pressure constricting the width of a human pelvis.
Our
ancestors first descended from the trees to scavenge meat from lions’
kills. Eventually, they began to
hunt. Their strategy was to exhaust and
bewilder their prey, hoping to use the local geography to assist in each
kill. Mammoths were more likely to fall
to their deaths than be slain by hurled spears; mounds of butchered bones
accumulated at the base of particularly useful cliffs.
The high
caloric density of cooked meat allowed our brains to expand … but the embrace
of hunting also caused more women to die in childbirth.
And, less
tragically, our upright posture distorts our understanding of the trees that
once harbored our communities. After
all, we live in our heads. It seemed
sensible to us that the most interesting life of a tree would transpire in its
loftiest branches.
Our
biology doesn’t force us to view the world a certain way, but it
dictates which perspectives are easiest to take.
Because our brains are story-generating organs, human cultures invariably see time as flowing uniformly in a single direction. But for subatomic particles, time appears to be symmetrical; the Feynman diagram of an interaction would appear perfectly plausible progressing either forward or backward.
Only our
universe’s progression toward greater entropy, i.e. randomness, seems to
introduce a directionality for time’s arrow.
But there’s no a priori reason to expect a world to progress
toward higher entropy. This
directionality seems to exist only because our particular universe happened to
be in an unstable, low entropy state shortly after the Big Bang.
Or so
say most physicists. From my
perspective, I’m content assuming that the past is fixed but the future is
mutable. If I didn’t believe in that
asymmetry – whether it’s real or not – I’d probably lapse into despair.
But,
again, even if we accept that time is flowing, our perspective alters how we
feel about that change.
Is the
flow of time progress or decline?
Are a
tree’s branches its hands or its feet?
In
Indian mythology, time is cyclical, but within each cycle it flows toward
corruption. Time passes and the world
grows worse. Currently we are trapped
within a Kali Age, the worst possible world, knowing that all the great heroes
have passed. We are just biding our time
before the world can be destroyed and made good again.
After
the sunder, time will once again cause that new world’s gleam to fade. Nothing can stave off the encroach of rot.
In
Judaism, the ancient sages lived longer than we do, and knew more, too. At one point in time, a pair of humans were good:
before long, we disobeyed the whims of God and were exiled from paradise.
In The
Book of Shem, David Kishik writes that
To be
original means to linger by the origin and insist on it. The task is to avoid the progression toward a
future or an end, and to stop the narrative before it develops any
further. In this sense, and in this
sense only, the origin is a worthwhile goal.
Hence in Hebrew forward (kadima) is related to what is ancient (kadum),
just as backward (achora) is linked to what is last (acharon).
Many
humans want to reclaim the imagined glories of the past.
To make
America great again, perhaps.
I
personally think that many recent technological developments in our world are
bad. We’ve designed distracting,
addicting telephones, and we’re putting them into the hands of children. Our brains evolved to be extremely plastic,
which let our species adapt to a wide variety of circumstances … but this
neural plasticity allows exposure to fabulous, drug-like devices to
dramatically alter our brains, probably for the worse.
And
we’ve designed distracting, addicting advertising platforms – these siphon huge
amounts of money away from productive industries, and the perverse economic
incentives we’ve constructed allow these companies, alongside equally-unhelpful
investment banks, to lure many of the most clever college graduates to their
ranks.
But I’m certainly no Luddite, pining for a purer past. The world was a terrible place for so many people. Although I appreciate the thesis that Yuval Noah Harari presents in Sapiens– that the invention of agriculture made people’s lives worse than when all humans were hunters and gatherers – I see those grim millennia as akin to the hump in a chemical reaction, a transition that must be traversed in order to reach the desired products.
For
generations, most people scraped out a miserable existence by subsistence
farming. Their lives were worse than
their ancestors’. But we, now,
can feed so many people so easily that we could make our world into a paradise.
We’re
not doing it, but we could.
At least we’re making baby steps toward a society in which people aren’t punished for their genetic background, or gender, or religious beliefs. I mean, even in the United States we still treat women shabbily; across the country, racist police departments beleaguer Black citizens; atheists and Muslims are eyed with distrust.
But it
used to be worse.
And, sure, even if we were the best of stewards, our planet would eventually be doomed. Even if we don’t exhaust the resources here on Earth, the sun will run out of energy and bloat to engulf our world in a ball of fire. Maybe that’s fine. Death is a part of my life; perhaps I should look upon extinction as a natural part of humanity’s journey through time.
But it’s
so cool to image people someday spreading amongst the stars. I dream about the future. And hope against hope – despite overpopulation,
climate change, and all – that my children will find a better world than the
one I’ve been living in.
From my
perspective, time will let us make the world better.
Although
it surely won’t happen on its own. We
will have to work to make it better. The
work might not be that hard. Just live
the way you would if the world were already the place it ought to be.
When a
scientist first discovers a function for a gene, that scientist gets to name
it. Sometimes these names seem
reasonable enough: I worked with a hematologist who did a study to identify
proteins involved in apoptosis, which means roughly “programmed cell death” or
“cellular suicide,” and so each gene wound up named “Requiem 3”, “Requiem 4,”
etc.
Fruit
fly geneticists tend to give their discoveries more creative names than other
scientists. There’s the gene “cheap
date” – if a fruit fly is missing that gene, it will – ha ha – be unable
to process ethanol and so quickly passes
out. Another genetic mutation produced
male flies that would court either males or females, and so this was known for
over a decade as “fruity,” until another scientist decided that universal
courtship could be less offensively described by the term “fruitless,”
because clearly any mating-like activity that does not lead to progeny is a waste of time.
Yup, some gene names were bad. One person’s idea of a joke might seem to somebody else like a mean-spirited reference to the wider world’s power dynamics.
Other
gene names were bad not out of malice, but because humor at the expense of a
fruit fly doesn’t make as many people laugh when a human child is dying.
A gene that produces a somewhat spiky-shaped protein was named after Sonic Hedgehog. It seemed funny at the time! See? The protein is spiky, the video game character has spiky hair, and … get it? You get it, right?
Okay, so this Sonic Hedgehog protein doesn’t look all that much like Sonic the Hedgehog. But spend enough time staring at something like protein crystal structures and you’ll experience pareidolia, like seeing animal shapes in irregularly dappled plaster ceilings, or anthropomorphic gods amongst the twinklings of the stars.
Well, the
Sonic Hedgehog protein establishes a concentration gradient that allows cells
to recognize their spatial position in a developing body. If a human fetus comes to term despite having
a mutation in the Sonic Hedgehog gene (genetic abnormalities will often result
in a miscarriage, but not always), the resulting child will have severe brain
defects.
And then
a doctor has to explain, “Your baby is suffering because of a Sonic Hedgehog
mutation.”
And so, in 2006, geneticists capitulated to medical doctors. No more fanciful names for genes that might lie at the root of human health problems … which, because humans and fruit flies are actually pretty similar, means most genes. Patients would now be told about a mutation in the SHH gene instead of Sonic Hedgehog, or a mutation in the LFNG gene instead of Lunatic Fringe.
Words have power, after all.
Some
people are more attentive to their environments than others. During evolutionary time, this trait was
obviously good for humanity. If your
tribe is traveling through a hostile environment, it helps to have somebody
around who is paying attention to the world.
A friend who’s primed to notice encroaching threats like a hungry lion
about to leap out and attack. Maybe
we should take a different path.
Which, yeah, that sounds like a good idea.
Other
people are particularly inattentive to their surroundings, so it’s easy
for them to ignore the world and focus instead on one single problem. During evolutionary time, this trait was
surely good for humanity, too. It’s helpful
to have somebody on the lookout for threats that might eat you, obviously. But it’s also helpful to have somebody who
might discover a way of using dried grass to weave baskets. A way of cooking mud into pottery that could
carry or store water.
Neurodiversity is a virtue in and of itself. Over the millennia, the world has offered our species many challenges. Populations that were sufficiently diverse that some members were good at each of a variety of tasks were most likely to flourish. A cooperative species like termites or Homo sapiens benefits from specialization among its members.
Left to
our their own devices, people would naturally fall asleep and wake up at
different times. Some brains are primed
to work best in the early morning; others work best late at night. And that’s good. It reduces the amount of time that a tribe
would be susceptible to attack, everyone asleep.
But in
the modern world, we occasionally forget to feel grateful for the diversity
that allowed our species to thrive. The
high school students whose brains are primed for late-night thinking drag
themselves through morning classes like zombies. They’ll be midway through first period before
the sun rises. Their teachers glance
derisively at their slumped and scruffy forms and call them lazy.
Eventually,
humans invented language. Much later, we
invented writing. Much, much later, we
invented the printing press, and then written words became so widely accessible
that most humans could benefit from learning how to read.
Of
course, reading is easier for people who are inattentive to their environment.
If I had been born earlier in human evolution, I totally would have been lion bait. When I’m reading a book, or am deep in thought, the rest of the world melts away. When I’m typing at home, K or the kids sometimes shout my name several times before I even realize that I’m being spoken to.
People like me, or this kid at a library, totally would’ve been lion bait.
Luckily for me, I wasn’t born way back then. Instead I was born into a world where inattentive people – the people best able to block out the world and instead focus on their own thoughts – are the most likely to find academic success. People like me become medical doctors. Then we get to name the world’s various conditions and maladies.
And so,
when it came time to categorize the sort of person who is especially attentive
to the world, people like me (who obviously thought that our way of
being is the best way to be) referred to those others as having an attention deficit
disorder.
Identifying
those people’s awareness of their environs might sound like a virtue; instead,
we castigated those people’s difficulty at ignoring the world.
I’ve
never read the Percy Jackson books, but I’m glad that they exist, if only for
passages like this (from The Lightning Thief):
“And the
ADHD – you’re impulsive, can’t sit still in the classroom. That’s your battlefield reflexes. In a real fight, they’d keep you alive. As for the attention problems, that’s because
you see too much, Percy, not too little.”
Childhood
trauma can cause symptoms that medical doctors term “attention deficit
disorder.” Which makes sense – if you’ve
gone through an experience where your environs were threatening, you should
learn to be more aware of your environment.
It should become more difficult to ignore a world that has proven
itself to be dangerous.
Even for
somebody with my type of brain, it’s going to be easier to sit outside
and read a book when there’s a squirrel nearby than if there’s a prowling
grizzly fifteen meters away.
Some
children have to learn early on that daddy’s sometimes a grizzly. And if it can happen to him, why not other
grown-ups, too? Best to stay on high
alert around the teacher. She’s trying
to get you absorbed in these number tables … but what if that’s a trap?
Certain drugs can narrow a person’s perception of the world. They act like blinders, chemicals like nicotine, ritalin, and amphetamines, both un-methylated (sold under the trade name Adderall) and methylated (a CH3 group attached to the amine moiety of Adderall will slow its degradation by CYP2D6 enzymes in the liver, increasing the duration of its effects).
Note to non-chemists: the methylated analogue of Adderall goes by several names, including “ice,” “shard,” and “crystal meth.” Perhaps you’ve heard of it — this compound played a key role in the television show Breaking Bad. And it’s very similar to the stuff prescribed to eight year olds. Feel free to glance at the chemical structures, below.
In
poetry class last week, a man who has cycled in and out of jail several times
during the few years I’ve taught there – who I’d said “hello” to on the outside
just a few weeks earlier when he rode his bicycle past the high school runners
and me – plonked himself down in the squeaky plastic hair next to mine.
I
groaned.
“I know,
I know,” he said. “But I might be out on
Monday.”
“What
happened?”
“Failed
a urine screen. But I was doing
good. Out for six months, and they were
screening me like all the time, I only failed three of them.”
“With …
?”
“Meth,”
he said, nodding. “But I wasn’t hitting
it bad, this time. I know I look like I
lost some weight, dropped from 230 down to 205, but that’s just cause it was
hard getting enough to eat. Wasn’t like
last time. I don’t know if you remember,
like, just how gaunt my whole face looked when they brought me in. But, man, it’s just … as soon as I step
outside this place, my anxiety shoots through the roof … “
This is
apparently a common phenomenon. When we
incarcerate people, we carve away so much of their experience of the
world. Inside the jail, there is a set
routine. Somebody is often barking
orders, telling people exactly what to do.
There aren’t even many colors to be distracted by, just the
white-painted concrete walls, the faded orange of inmate scrubs, the dull tan
CO shirts and dark brown pants.
The
world in there is bleak, which means there are very few choices to make. Will you sit and try to listen to the
TV? (The screen is visible from three or
four of the twelve cells, but not from the others.) Try, against all odds, to read a book? Or add your shouting voice to the din, trying
to have a conversation (there’s no weather, so instead the fall-back topic is
speculating what’s going to be served for dinner)?
After
spending time locked up, a person’s ability to navigate the wider world
atrophies, the same as your leg would if you spent months with it bundled up in
a cast.
And
these are people whom we should be helping to learn how to navigate the world better.
“ … so I
vape a lot, outside. I step out of this
place, that’s the first thing I do, suck down a cigarette. And, every now and then … “
He feels
physically pained, being so attentive to his surroundings. And so he doses himself with chemicals that
let him ignore the world as well as I can.
And,
yes. He grew up with an abusive
stepfather. This led to his acting
squirrelly in school. And so, at ten
years old, medical doctors began dosing him with powerful stimulants.
Meanwhile, our man dutifully internalized the thought that he had a personal failing. The doctors referred to his hyper-vigilance as an attention deficit disorder.
Words
have power.
We can’t
know now, after all the hurt we’ve piled on him, but think: where might our man
be if he’d learned to think of his attentiveness as a virtue?
Frank Brown Cloud 
