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.
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.
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.
When we were in college,
my roommate and I spent a train ride debating the merits of Andy Warhol’s art
(she was a fan, I was not). In the end,
we not only failed to change each other’s opinions, but realized that we didn’t
even agree what art was. She
double majored in Biomedical Engineering and Art Theory & Practice, and her
view was much more expansive than my own.
In retrospect, I can admit
that she was right. My view of art was
narrow-minded. If I had to proffer a
definition of “art” today, I might go with something like:
Art is an
intentionally-created module that is designed to reshape the audience’s neural
architecture.
By this standard, the big
images of soup qualify. So do the
happenings.
Andy Warhol’s “Campbell’s Soup Cans,” 1962. Image by Wally Gobetz on Flickr.
I recently read a book that analyzed board games using the tools of art criticism and narratology. Obviously, I now think that board games can be art. They’re carefully designed; their creators often seem to have a goal for how each game should make players feel; the combined effects of text, visual components, and even rules can all work toward conveying those feelings.
One drawback to my
newfound open-mindedness, though, is that I could probably be convinced that
almost any designed object qualifies as art.
For a piece of art to
“fail” to change your neural architecture, it would have to be mnemonically
invisible – immediately after seeing it, you could look at it again and it
would be as though it were the first time.
You’d never be able to recall its content or meaning.
Actually, I have
read some esoteric, convoluted poetry like that. Words that skimmed over my mind as though
each synapse were coated with teflon.
I wasn’t keen on the
experience. Minutes had passed, but,
because I couldn’t remember anything that I’d read, I’d accomplished
nothing. I don’t need to actually understand
a poem, I just want for it to make me feel somehow different after I’ve read
it. Like Will Alexander’s “The Optic
Wraith,” which triggers a mysterious sense of unease even though its meaning
squirms away from me:
The Optic Wraith
Her eyes
like a swarm of dense
volcano spiders
woven from cold inferno
spools
contradictory
consuming
clinging to my palette
like the code from a bleak
inventive ruse
now
my understanding of her
scent
is condoned as general
waking insomnia
as void
as a cataleptic prairie
frayed at the core
by brushstrokes of vertigo
then mazes
…
As Alexander’s words lure
me along, I lose my grasp. But although
I might not recall any specific lines, if you asked me at the end of its six
pages, “So, what did you feel?”, I’d certainly know that something inside my
brain was different from who I’d been five minutes before.
When I was in college, I
felt strongly that art needed to be beautiful.
I was wrong. But I still believe
that art works better when it’s aesthetically pleasing, because this allows it
to more readily infiltrate someone’s mind.
If two paintings are both intended to convey the same ideas, but one is
more pleasurable to look at, then we can assume that it will be looked at more,
and thereby convey the idea more.
A charming form helps the piece achieve its function of spreading the
creator’s intended message.
And, in terms of judging
the quality of art, I obviously still think that the quality of message is
important.
For instance, a
chair. Every chair you’ve ever sat in
was designed by somebody. If you
wanted to argue that the chair is a piece of art, I suppose I’d agree with
you. And maybe it’s a very good chair:
comfortable to sit in, perfectly balanced, pleasing to see when the rising sun
illuminates it in the morning. But that
doesn’t mean it’s good art.
Joseph Kosuth’s “One and Three Chairs,” 1965. Photo by Kenneth Lu on Flickr.
Indeed, a chair that is bad at being a chair is more likely to be a good artwork. A chair that’s too small or too large, conveying the discomfort of trying to make your way in a world that is primarily concerned with the comfort of bodies unlike your own. Or a gigantic bronze throne that affords you the chance to perch in Baphomet’s lap; it would be an unpleasant place to sit, but perhaps you’d reflect more on Lucifer’s ethic of “speaking truth to power, even at great personal cost.”
When we humans make art,
we try to engage the emotions of our audience.
Emotionally-charged situations are more memorable; while feeling awe, or
anger, or joy, human minds are most likely to change.
And human art is almost always made for a human audience. Our brains evolved both from and for gossip; our prodigious intellect began as a tool to track convoluted social relationships. We’re driven to seek narrative explanations, both because a coherent story makes gossip easier to understand, and because our consciousness spins stories to rationalize our actions after we perform them.
If we considered the world’s most intelligent animal species – like humans, dolphins, crows, elephants, chimpanzees – most have evolved to gossip. Large brains gave our ancestors a selective advantage because they were able to track and manipulate their societies complex social relationships in a way that bolstered survival and breeding opportunities. Indeed, the average elephant probably has more emotional intelligence than the average human, judging from neuron counts in the relevant areas of each species’ brains.
Elephants at a sanctuary. Image by Gilda on Flickr.
And so, if an elephant were given the freedom to paint (without a trainer tugging on her ears!), I imagine that she’d create art with the intention that another elephant would be the audience. When a chimpanzee starts drumming, any aesthetic message is probably intended for other chimpanzees.
But what about octopus
art?
Octopuses and humans haven’t had any ancestors in common for half a billion years. Octopuses are extremely intelligent, but their intelligence arose through a very different pathway from most other animals. Unlike the world’s brilliant birds and mammals, octopuses do not gossip.
Octopuses tend to be antisocial unless it’s mating season (or they’ve been dosed with ecstasy / MDMA). Most of the time, they just use their prodigious intellect to solve puzzles, like how best to escape cages, or find food, or keep from being killed.
Octopus hiding in two shells. Image by Nick Hobgood on Wikipedia.
Humans have something termed “theory of mind”: we think a lot about what others are thinking. Many types of animals do this. For instance, if a crow knows that another crow watched it hide food, it will then come back and move the food to a new hiding spot as soon as the second crow isn’t looking.
When we make art, we’re
indirectly demonstrating a theory of mind – if we want an audience to
appreciate the things we make, we have to anticipate what they’ll think.
Octopuses also seem to have a “theory of mind,” but they’re not deeply invested in the thoughts of other octopuses. They care more about the thoughts of animals that might eat them. And they know how to be deceptive; that’s why an octopus might collect coconut shells and use one to cover itself as it slinks across the ocean floor.
A coconut octopus. Image by Christian Gloor on Wikimedia.
Human art is for humans, and bird art for birds, but octopus art is probably intended for a non-octopus audience. Which might require even more intelligence to create; it’s easy for me to write something that a reader like me would enjoy. Whereas an octopus artist would be empathizing with creatures radically different from itself.
If octopuses weren’t stuck
with such short lifespans, living in the nightmarishly dangerous ocean depths,
I bet their outward focus would lead them to become better people than we
are. The more we struggle to empathize
with others different from ourselves, the better our world will be.
Frank Brown Cloud 
