Future Evolution- how will the human species evolve in the next 10,000 years?

Studying humanity’s past is the best way to predict our evolutionary future- but what it tells us is strange, surprising, and a little scary.

We’re the unlikely result of four billion years of evolution.

From self-replicating molecules in Archean seas, to eyeless fish in the Cambrian deep, to mammals scurrying from dinosaurs in the dark, and then, finally, improbably ourselves – evolution shaped us.

Organisms reproduced imperfectly. Mistakes made when copying genes sometimes made them better fit to their environments, so those genes tended to out-reproduce other DNA sequences. More reproduction followed, and more mistakes, the process repeating over billions of generations. Finally, Homo sapiens appeared. But we aren’t the end of that story. Evolution won’t stop with us, and we might be evolving faster than ever.

How will we evolve?

It’s hard to predict the future. The world will probably change in ways we can’t imagine. But we can make educated guesses. Paradoxically, the best way to predict the future is probably looking at the past, and assuming past trends will continue going forward. And this suggests some surprising things about our future.

We’re likely to live longer, become taller, and more lightly built. We may become more attractive. We’ll be less aggressive, and more agreeable, but with smaller brains. Imagine a species of tall, willowy, long-lived supermodels. We’ll be beautiful, but with the personality of a Golden Retriever- friendly, maybe not that bright. At least, that’s one possible future. But to understand why I think this is likely, we need to look at biology.

Will we turn into a race of supermodels?

The end of natural selection?

Some scientists have argued that civilisation’s rise ended natural selection. It’s true that the selective pressures that dominated in the past - predators, famine, plague, warfare – have mostly disappeared.

Starvation and famine were largely ended by high-yield crops, fertilisers, and family planning. Violence and war are less common than ever, despite modern militaries with nuclear weapons, or maybe because of them. The lions, wolves, and sabertoothed cats that hunted us in the dark are endangered, or extinct. Plagues that carried off millions – smallpox, Black Death, cholera – were tamed by vaccines, antibiotics, clean water.

But evolution didn’t stop; other things just drive it. Evolution isn’t so much about survival of the fittest as reproduction of the fittest. So even if Nature is less likely to murder us, we still need to find partners, and raise children - so sexual selection now plays a bigger role in evolution.

And if Nature no longer controls our evolution, the unnatural environment we’ve created - culture, technology, cities - creates new selective pressures very different from those we faced in the Ice Ages. We’re poorly adapted to this modern world, therefore, we’ll adapt. It’s already happening. As our diets changed to include grains and dairy, we evolved genes to help us digest starch and milk. When dense cities created conditions for disease to spread, mutations for disease resistance spread too. And- for reasons we don’t know- our brains have gotten smaller. Unnatural environments create unnatural selection.

To predict where this goes, we’ll look at our prehistory, studying trends over the past 6 million years of evolution. Some of these trends will continue, especially trends seen in the past 10,000 years, after agriculture and civilisation were invented. We’ll also face new selective pressures, like reduced mortality. Studying the past doesn’t help here, but we can study how other species responded to similar pressures. Evolution in domestic animals may be especially relevant- arguably we’re becoming a kind of domesticated ape, but curiously, one domesticated by ourselves. Using this approach, I’ll make some predictions— if not always with high confidence. That is, I’ll speculate.

Lifespan

Humanity will almost certainly evolve to live longer- much longer. Life cycles evolve in response to mortality rates, how likely predators and other threats are to kill you. With high mortality rates, animals must reproduce young, or might not reproduce at all. There’s also no advantage to evolving mutations that prevent aging, or cancer- you won’t live long enough to use them.

If mortality rates are low, the opposite is true. It’s better to take your time reaching sexual maturity. It’s also useful to have adaptations that extend lifespan, and fertility, giving you more time to reproduce. That’s why animals with few predators- living on islands, or the deep ocean, or simply being large- evolve longer lifespans. Greenland sharks, Galapagos tortoises and bowhead whales all mature late, and can survive for centuries.

Even before civilisation, humans were unique among apes in having low mortality and long lives. Hunter-gatherers armed with spears and bows could defend against predators; food sharing prevented starvation. So we evolved delayed sexual maturity, and the longest lifespans of any primate- up to 70 years.

Still, child mortality was high - approaching 50% or more by 15. So average life expectancy was just 35 years. Despite the rise of civilization, child mortality stayed high until the 19th century, while life expectancy went down- to 30 years- due to plagues and famines.

Then, over the past two centuries, better nutrition, medicine and hygiene reduced youth mortality to under 1% in most developed nations. Life expectancy soared to 70 years worldwide and 80 in the West.

In this environment, there’s little pressure to reproduce early. If anything, the years of training needed to be a doctor, CEO, or carpenter incentivize putting it off. And since life expectancy doubled, adaptations to prolong lifespan and child-bearing years are favored. Given that more and more people live to 100 or even 110 years-the record is 122 years- there’s every reason to think we could evolve to live more than a century.

Size, and strength

Animals often evolve larger size over time; it’s a trend seen in tyrannosaurs, whales, horses, and primates- including hominins.

Early hominins like Australopithecus afarensis and Homo habilis were small, four to five feet (120-150 cm) tall. Later hominins-Homo erectus, Neanderthals, Homo sapiens- grew taller. We’ve continued to gain height in historic times, partly driven by improved nutrition, but genes seem to be evolving too.

Why we got big is unclear. In part, mortality may drive size evolution; growth takes time, so longer lives mean more time to grow. But human females also prefer tall males. So both lower mortality and sexual preferences will likely cause humans to get taller. Today, the tallest people in the world are in Europe, led by the Netherlands. Here, men average 6 feet (183 cm); women 5 foot 6 (170 cm); someday, most people might be that tall, or taller.

Modern humans are more gracile than our stocky Neanderthal kin.

As we’ve grown taller, we’ve become more gracile. Over the past 2 million years, our skeletons became more lightly built as we relied less on brute force, and more on tools and weapons. As farming forced us to settle down, our lives became more sedentary, so our bone density decreased. As we spend more time behind desks, keyboards, and steering wheels, these trends will continue.

Humans have also reduced our muscles compared to other apes, especially in our upper bodies. That will probably continue. Our ancestors had to slaughter antelopes and dig roots; later they tilled and reaped in the fields. Modern jobs increasingly require working with people, words, code- they take brains, not muscle. Even for manual laborers- farmers, fisherman, lumberjacks- machinery like tractors, hydraulics, and chainsaws now shoulder lots of the work. As physical strength becomes less necessary, our muscles will keep shrinking.

Our jaws and teeth also got smaller. Early, plant-eating hominins needed huge molars and mandibles for grinding fibrous vegetables. As we shifted to meat, then started cooking food, jaws and teeth shrank. Modern processed food- chicken nuggets, Big Macs, cookie dough ice cream- needs even less chewing, so jaws will keep shrinking, and we’ll likely lose our wisdom teeth.

Beauty

After people left Africa 100,000 years ago, humanity’s far-flung tribes became isolated by deserts, oceans, mountains, glaciers, and sheer distance. In various parts of the world, different selective pressures - different climates, lifestyles, especially beauty standards- caused our appearance to evolve in different ways. Tribes evolved distinctive skin colors, eyes, hair, facial features. Swedes don’t look like Inuit or Andamanese; Mongolians don’t look like Bushmen or Bantu.

With civilization’s rise and new technologies, these populations were linked again. Wars of conquest, empire-building, colonization and trade- including the trade of other humans- all shifted populations, which interbred. Today, road, rail and aircraft link us too. Bushmen would walk 40 miles to find a partner, we’ll go 4,000 miles. We’re increasingly one, worldwide population, freely mixing. That will create a world of hybrids— light brown skinned, dark-haired, Asio-Euro-Afro-Australo-Amerindians, their skin color and facial features tending toward the global average.

As different ethnicities mix, humans are likely to get hotter

And these people will be beautiful. Mixed-race people are often seen as more attractive, likely because we find faces with average shapes more attractive than outliers.

Sexual selection will accelerate the evolution of our appearance. With most forms of natural selection no longer operating, mate choice will play a larger role. Humans might become more attractive, but more uniform in appearance. Globalised media may also create more uniform standards of beauty, pushing all humans towards a single ideal.

Youth is also attractive, so we may select for features suggestive of youth- large eyes, small noses and lips, round faces. Sex differences are likely to be exaggerated. Men will continue to select women on the basis of fertility- signaled by well-developed breasts and a high hip:waist ratio, exaggerating those features. Women will likely continue to select men for features like facial shape, facial hair, and broad shoulders.

Intelligence and personality

Last, our brains and minds, our most distinctively human feature— will evolve, perhaps dramatically. Over the past six million years, hominin brain size roughly tripled, suggesting selection for big brains driven by tool use, complex societies, language, or all three. It seems inevitable this trend will continue, but it probably won’t.

Instead, our brains are getting smaller. In Europe, brain size peaked 10,000—20,000 years ago, just before we invented farming. Then, brains got smaller. Modern humans have brains smaller than our Greek and Roman predecessors, even medieval people. It’s not clear why.

It may be that fat and protein were scarce once we shifted to farming, making it costly to grow and maintain large brains. Brains are also energetically expensive- they consume around 20% of our daily calories. In agricultural societies with frequent famine, a big brain might be a liability.

Maybe hunter-gatherer life was demanding in ways farming isn’t. In civilization, you won’t need to outwit lions and antelopes, memorize every fruit tree and watering hole in 1000 square miles, or the call of every bird. Making and using bows and spears also requires fine motor control, coordination, the ability to track animals and trajectories— maybe the parts of our brains used for those things got smaller.

Or maybe, living in a large society of specialists requires less brainpower than being in a tribe of generalists. Stone-age people mastered many skills- hunting, tracking, foraging for plants, making herbal medicines and poisons, crafting tools, waging war, music, magic. Modern humans play fewer, more specialised roles as part of vast social networks, exploiting division of labour. In a civilization, we specialize on a trade, then rely on others for everything else. The brewer brews beer, then relies on farmers, doctors, tailors, craftsmen, soldiers, and artists for everything else.

Brain size isn’t everything; elephants and orcas have bigger brains than us; and Einstein’s brain was smaller than average. How much it affects overall intelligence is unclear. Maybe we lost certain types of intelligence, and enhanced others. Still, I worry about what that missing 10% of my grey matter did.

Curiously, domestic animals also evolved smaller brains. Sheep lost 24% of their brain mass after domestication; for cows, it’s 26%, dogs, 30%. Which raises an unsettling possibility- maybe being less clever, more willing to passively go with the flow, like a domesticated animal, has been bred into us, like it was for them.

Our personalities must be evolving too. Hunter-gatherer life required aggression. Men hunted large mammals, killed over women, warred with other tribes. We get meat from a store, and turn to police and courts to settle disputes. If war hasn’t disappeared, it now accounts for fewer deaths, relative to population, than at any time in history. Aggression, now a maladaptive trait, will be bred out.

Changing social patterns will also change personalities. Humans evolved to live in larger groups than other apes, forming tribes of around 1,000 in hunter-gatherers. But today’s world is increasingly urbanized, with people living in vast, high-density cities of millions. In the past, our relationships were necessarily few, and often lifelong. Now we inhabit seas of people, moving often for work, in the process forming thousands of relationships, many fleeting- friendships, acquaintances, work partners, lovers- and increasingly, virtual relationships via text and internet. This world will push us to become more outgoing, open and tolerant. Yet navigating vast social networks may also require we become more willing to adapt ourselves to them- to be more conformist.

Not everyone is psychologically well-adapted to this existence. Our instincts, desires, and fears are largely those of stone-age ancestors, who found meaning in hunting and foraging for their families, warring with their neighbors, praying to their ancestor-spirits in the dark. Modern society meets our material needs well, but is less able to meet the psychological needs of our primitive caveman brains.

Sorrowing old man, by Vincent Van Gogh

Perhaps because of this, increasing numbers of people suffer from psychological issues like loneliness, anxiety and depression; many turn to alcohol and substances to cope. Selection against vulnerability to these conditions might improve our mental health, and make us happier as a species. But that could come at a price. Many great geniuses had their demons; leaders like Lincoln and Churchill fought with depression, as did scientists like Newton and Darwin, and artists like Herman Melville and Emily Dickinson. Some, like Virginia Woolf, Vincent Van Gogh, and Kurt Cobain, took their own lives. Others - Billy Holliday, Jimi Hendrix, Jack Kerouac– were destroyed by substance abuse.

A disturbing thought is that troubled minds and misfits will be removed from the gene pool— put potentially at the cost of eliminating the sort of spark that created visionary leaders, great writers, artists, and musicians. Future humans might be better adjusted — but less fun to party with, or talk music with, less likely to launch a scientific revolution— stable, happy, and boring.

Speciation

There were once nine human species, now it’s just us. But could new human species evolve? For speciation to happen, we’d need isolated populations subject to distinct selective pressures. Distance no longers isolates us, but reproductive isolation could be achieved by selective mating. If people segregated based on culture— intermarrying based on religion, class, caste, or even politics— distinct populations, even species might evolve.

Civilization made canines more diverse.

H.G. Wells, in The Time Machine saw a future where class created distinct species. Upper classes evolved into the beautiful, useless Eloi, and the working classes become the ugly, subterranean Morlocks— who revolted and enslaved the Eloi as food animals. In the past, religion has sometimes divided us- Jews became genetically distinct from other people due to intermarriage, for example. Lifestyle can also create isolation, as in the Gypsies, whose nomadic life separated them from settled people, making them genetically distinct. Today, politics divides us— could it divide us genetically? Liberals now move to be near other liberals, conservatives to be near conservatives; many on the left won’t date Trump supporters, and vice versa. Could Americans become two species, with instinctively different views on issues like religion, guns, and government? Probably not. Still, to the extent culture divides us, it could drive evolution in different ways, in different people. Diverse cultures will mean diverse genetics.

Strange New Possibilities

So far, I’ve mostly taken a historical perspective, looking back. But in some ways, the future might be radically unlike the past. Evolution itself has evolved.

One of the more extreme possibilities is directed evolution, where we actively control of our species’ evolution. The idea of selectively breeding humans like animal was first put forward by Plato, who felt society should favor reproduction of intellectually superior people (meaning people like Plato, of course). Following Darwin’s discovery of evolution, the idea of governments breeding humans was revived. The Eugenics (‘good genes’) movement, started in the UK, sought to improve the human gene pool— ultimately leading to forced sterilizations in the United States, and the killing of undesirables in Nazi Germany.

We’ve rejected the idea that governments should decide who reproduces or not. But arguably, humans have always practiced selective breeding. We breed ourselves, when we choose partners with appearances and personalities we like. And for thousands of years, hunter-gatherers arranged marriages, seeking good hunters for their daughters. Even where children chose partners, men were generally expected to seek approval of the bride’s parents. Such practice persists in the West- Pride and Prejudice opens not with two young lovers, but two parents trying to find husbands for their daughters. In other words, we breed our own children.

And going forward, we’ll do this with far more knowledge of what we’re doing, and more control over the genes of our progeny. We can already screen ourselves and embryos for genetic diseases. We could potentially choose embryos for desirable genes, as we do with crops. Direct editing of the DNA of a human embryo has been proven to be possible— but seems morally abhorrent, effectively turning children into subjects of medical experimentation. And yet, if such technologies were proven safe, I could imagine a future where you’d be a bad parent not to give your children the best genes possible.

The cake is a lie.

Computers provide an entirely new selective pressure. As more and more matches are made on smartphones, we are delegating decisions about what the next generation looks like to computer algorithms, who recommend our potential matches. Digital code now helps chose what genetic code passed on to future generations, just like it shapes what you stream or buy online. That might sound like dark science fiction, but the current generation are the first to be bred using the assistance of computers. Our genes are being curated by computer, just like our playlists. It’s hard to know where this leads, but I wonder if it’s entirely wise to turn over the future of our species to iPhones, the internet, the cloud.

Discussions of human evolution are usually backward looking, as if the greatest triumphs and challenges were in the distant past. But as technology and culture enter a period of accelerating change, our genes will too. Arguably, the most interesting parts of evolution aren’t life’s origins, dinosaurs, or Neanderthals, but what’s happening right now, our present- and our future. Whether you study our species as a biologist, our just as a fellow member of it, we live in interesting times.