On the evolution of skin color.

On the evolution of skin color.

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. 

Or so ruled our Supreme Court.

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.

A photograph showing a book page in Icelandic.

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.

A Wiccan-style gathering of artifacts including a statue of a seated green goddess, her pregnant belly painted as the earth; mums; a chalice; a string of green beads; a stoppered rectangular prism bottle; and a candleholder appearing to be carved of wood, again of a pregnant woman with hands holding her belly.

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.

A sun-dappled photograph of a page of the Bible.

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. 

A photograph of a model dinosaur, complete with feathers.

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.

A photograph of a three-spined stickleback fish.

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.

Image shows the upright skeletal postures of gibbons, humans, chimpanzees, gorillas, and orangutans.

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.

A sculpture of a dodo.

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.

Everyone living today is human.  We are all Homo sapiens, all the same species.  But some of us do carry vestiges of the other human populations whom our ancestors killed.

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.

Blue sky and white cirrus clouds as viewed through coiled razor wire atop a barbed-wire fence.

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.

Pottery shard depicting a boar hunt in ancient Greece.

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.

On the sounds of aberrant ecosystems

On the sounds of aberrant ecosystems

When I was ten years old, I read about a new card game, Magic, in the local newspaper. The article described the basic conceit of the game – you are a wizard who must conquer territory to power your spells – and a few of the cards – the article mentioned Giant Growth, which it said “is just a big rat.”

squeeI was enthralled. It took about a year of searching before I found a place to buy cards, but eventually the local hobby shop would siphon away all my babysitting money.

My favorite card was Squee – a goblin who keeps returning from the dead. Squee was pretty powerful when combined with Survival of the Fittest, which lets you trade your weak creatures for more powerful monsters, and Goblin Bombardment, which lets you fling creatures at your enemies. But I loved Squee disproportionately to his power. This little monster, swimming in his robes, is blessed with infinite renewal … just like humanity’s original misconception of nature.

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Before the industrial revolution, no single generation could change the world enough to prove this notion wrong. Humans cut down trees, but there are so many trees and more grow all the time. Humans wash their clothes or defecate in the river, but new clean water flows. Humans hunt game and catch fish, but – as long as you make a god-placating sacrifice every now and then – there will always be more animals to eat.

sunshot.JPG

Jared Diamond remarks upon our inability to notice slow changes in Collapse, his (tragically relevant) account of the factors that cause civilizations to die:

collapseI suspect that landscape amnesia provided part of the answer to my UCLA students’ question, “What did the Easter Islander who cut down the last palm tree say as he was doing it?” We unconsciously imagine a sudden change: one year, the island still covered with a forest of tall palm trees being used to produce wine, fruit, and timber to transport and erect statues; the next year, just a single tree left, which an islander proceeds to fell in an act of incredibly self-damaging stupidity. Much more likely, though, the changes in forest cover from year to year would have been almost undetectable: yes, this year we cut down a few trees over there, but saplings are starting to grow back again here on this abandoned garden site. Only the oldest islanders, thinking back to their childhoods decades earlier, could have recognized a difference. Their children could no more have comprehended their parents’ tales of a tall forest than my 17-year-old sons today can comprehend my wife’s and my tales of what Los Angeles used to be like 40 years ago. Gradually, Easter Island’s trees became fewer, smaller, and less important. At the time that the last fruit-bearing adult palm tree was cut, the species had long ago ceased to be of any economic significance. That left only smaller and smaller palm saplings to clear each year, along with other bushes and treelets. No one would have noticed the falling of the last little palm sapling.

It probably took several generations before trees were expunged from Easter Island. As Homo sapiens migrated into Europe, the Americas, and Australia, most large animals were driven to extinction, including all other species of humans. The Homo sapiens involved probably had no idea what they were doing. Each generation would see some decline in the abundance of an animal, but nothing to worry about. The last few deaths would occur among a people who had no idea what was lost.

Moby_Dick_p510_illustrationIn Herman Melville’s Moby Dick, the narrator considers whether Leviathan can long endure so wide a chase, and so remorseless a havoc; whether he must not at last be exterminated from the waters, and the last whale, like the last man, smoke his last pipe, and then himself evaporate in the final puff.

The narrator promptly dismisses this fear. Yes, buffalo were driven to extinction in America, but only because a single man could slaughter thousands. At that time, the concerted efforts of many were needed to kill each whale.

Even so, the whales seemed to be disappearing. But the narrator – so obsessed with the hunt that he hardly notices when he’s deluding himself – rejects the evidence:

10838762315_69b85f2e8a_zAnd equally fallacious seems the conceit, that because the so-called whale-bone whales no longer haunt many grounds in former years abounding with them, hence that species also is declining. For they are only being driven from promontory to cape; and if one coast is no longer enlivened with their jets, then, be sure, some other and remoter strand has been very recently startled by the unfamiliar spectacle.

Sperm whale populations plummeted. Gestation lasts over a year; mothers care for their young for a decade; males sexually mature at eighteen and aren’t fully grown until their fifties. They could not reproduce as quickly as we could kill them.

1024px-Mother_and_baby_sperm_whale.jpg

Most whales are extremely social, and communicate in ways that humans don’t yet understand. Their songs show signs of local culture, as do their hunting strategies. Those centuries of “harvest” may have caused several dialects or languages to be lost.

Sperm whale populations have since recovered. But several other species of whale are endangered. Our discarded plastics waft through the sea. The waters are becoming sufficiently acidic to kill off coral reefs.

The ocean is not nearly so infinite as we humans once thought it to be.

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Recently, technological progress has become so fast that the world changes noticeably within single generations. For tens of thousands of years, each human’s life resembled that of the parents. Even after some humans developed an agrarian lifestyle and began curating the evolution of favored plants and animals, the world changed slowly. Over many generations, Zea mays went from a useless scruffy grass to buxom-kernaled ears of corn. But, over the course of any single farmer’s life, the corn gnawed during senescence could probably be mistaken for the corn of youth.

Whereas my grandmother’s cellphone / camera / computer combo looks radically different from any of the bulky, ineffectual devices available when she was young. And my parents’ generation – whose lives spanned the development of modern agricultural practices – has seen a precipitous fall in all non-human animal life. In The Moth Snowstorm, Michael McCarthy describes this decline:

The_Moth_Snowstorm_for_web_df271fb2-a6f7-4703-9f9a-23ea2dbb7f70_1024x1024It had been the most powerful of all the manifestations of abundance, this blizzard of insects in the headlights of cars, this curious side effect of technology, this revelatory view of the natural world which was only made possible with the invention of the motor vehicle. It was extraordinary; yet even more extraordinary was the fact that it had ceased to exist. Its disappearance spoke unchallengeably of a completely unregarded but catastrophic crash in Britain of the invertebrate life which is at the basis of so much else. South Korea may have destroyed Saemangeum, and China may have destroyed its dolphin, but my own country has wrecked a destruction which is just as egregious; in my lifetime, in a process that began in the year I was born, in this great and merciless thinning, it has obliterated half its living things, even though the national consciousness does not register it yet. That has been my fate as a baby boomer: not just to belong to the most privileged generation which ever walked the earth, but, as we can at last see now, to have my life parallel the destruction of the wondrous abundance of nature that still persisted in my childhood, the abundance which sang like nothing else of the force and energy of life and could be witnessed in so many ways, but most strikingly of all in the astonishing summer night display in the headlight beams, which is no more.

Cleaning splattered bugs off a windshield doesn’t sound like fun; drivers rarely have to do this anymore. But … we now have only a tenth as many insects as we did during the 1980s. Which means a tenth as much food for birds: their populations are falling too. Birds breed more slowly now, for lack of food, and many are killed off because our world sports unnaturally high population densities of predatory cats.

And that’s just the decline since 1989. Over the course of McCarthy’s life, insect populations may have fallen by 95% or more. And, because of the “landscape amnesia” described by Diamond above, it’s difficult for anyone born later to even realize what’s been lost. We assume that whatever world we’ve been born into is normal.

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Last night, Uncle Max woke me to go outside at 3 a.m. Afterward, I lay in bed listening to the birds singing.

Fewer birds sang at night when I was growing up. But they are adapting to our world. Our streetlights shine all the time, and our cities, during the day, are so loud that their songs cannot be heard. Humanity’s persistent racket is infiltrating even the most secluded corners of the world.

From Ula Chrobak’s article on noise pollution:

noiseSome plants need silence for seed dispersal—revving cars can scare away rodents that might otherwise do the job. Animals need silence to hear predators approaching or to communicate with their mates: A bird whose song would normally travel 100 meters would, with a 10-fold increase in noise, have its melody stifled to a 10-meter radius. “In so many landscapes, both people and other organisms are living in shrunken perceptual worlds,” says [ecologist] Clinton Francis.

In The Songs of Trees, David Haskell describes the way our forests should sound – the natural world has its own rhythms, its own music. In the following passage he listens in the Amazon:

songsoftreesA tinamou sings the forest’s vespers. Although this turkey-size relative of the emu is seldom seen, its melodies accent every dusk. The sound is the work of a silversmith, pure tones that the artist melts and crafts into ornament. The inflections and timbre of the Andean quena flute are surely inspired by the songs of these birds. In the understory the dark is comprehensive, but here in the ceibo crown, dusk lingers another thirty minutes, the orange gray western light of sunset reaching us unobstructed as we hear the tinamou’s song.

As the light drains, bromeliad frogs spasm chuckles and grunts from aerial ponds. They call for five or more minutes, then cut to silence. Any sound will set them off again: a stray frog call, a human voice, the bleat of a roosting bird trodden by a companion. Three species of owl join the frogs. Crested owls punch regular groans from below, keeping in touch with mates, neighbors, and the youngster that the pair have hidden in the low branches of an Inga tree. The spectacled owl’s repeated low, rubbery calls wobble around their crooked axis like a badly aligned tire. A distant tawny screech owl sings a high to-to-to-to, an endless, jabbing ellipsis. Insects pulse high drills, clear, sweeping chirps, saws, and tinkles. Monkeys and parrots whose sounds dominate the day have dozed away. The upper leaves of the ceibo chuff in the sharp gusts that accompany the sunset, then the wind eases and stillness comes to the tree.

But these forests, too, are threatened. The ancient trees are cut down and the music wanes. One after another, pockets of nature are forgetting how to speak. Again from Haskell:

In the center of town, Quichua men in suits work with and within the local government. The central, national government hurts and kills the ceibo mother tree, cutting her away piece by piece. Even conservation programs encourage people to cut away the trees. We lose our medicines and hunting. State-driven conservation erodes the indigenous community. Without intact territory, owned and managed by the indigenous community, the forest falls into incoherence, the community dies.

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The evidence of harm is all around us. Our world sounds wrong, tastes wrong, smells wrong. We’re scraping too few bugs off our windshields after long drives.

And, if we don’t act, our children won’t feel that they need to. A hot, loud planet will feel just as normal to them as the planet we inherited felt to us.