TIME Research

Humans and Neanderthals Were Actually Neighbors

Paleontologists know plenty about our nearest human cousins, the Neanderthals. They know that this highly successful species walked the Earth for some 300,000 years (we’ve been around for less than 200,000). They know the Neanderthals kept their caves surprisingly tidy; that they ate things other than raw meat; that they practiced recycling, wore jewelry and were generally much more sophisticated than their popular reputation would suggest.

Yet it didn’t take long after our own species invaded their last known outpost in Europe that the Neanderthals went utterly extinct. Now a new paper in Nature suggests it happened over a period of between 2,600 and 5,400 years or so—which is twice as fast as anyone had thought. The two groups did, evidently, coexist: “They lived in Europe at the same time,” says lead author Tom Higham, of Oxford, “although they were spatially separated. It was like a mosaic.” Agrees William Davies, of the University of Southampton, who wrote a commentary on the new research, also in Nature, “It’s not a neat story. It’s quite complex.”

The key to the new analysis was an unusually large sample of human and Neanderthal remains from 40 different sites across Europe, along with improved methods for filtering out contaminants from the samples before attempting to date them. In many cases, the remains weren’t bones but rather stone tools thought to characteristic of one species or the other—so-called Mousterian and Châtelperronian tools for the Neanderthals and Uluzzian tools for our own ancestors.

That raises, if not a red flag, then at least a sort of pinkish one, according to Davies. “In the old days, we had very few assemblages of tools, so it was quite easy to say that Mousterian tools represented Neanderthals, while tools with longer blades reflect anatomically modern humans.” But with more and more tools in their collections, paleontologists have become less sure. “The whole thing has become more blurred and less certain.”

The new analysis doesn’t depend entirely on who made what tools, however, and, says Davies, “the areas they’ve chosen to analyze are places where we can be more confident than most.” What makes the work so potentially important, he says, is that it gives a much finer-grained picture than ever before of where Neanderthals and modern humans lived and when, and how those patterns changed as Neanderthal numbers dwindled, then vanished.

That in turn will help anthropologists figure out how the Neanderthals vanished—what force or forces drove them extinct by about 40,000 years ago. “We think the Neanderthals had very low population numbers when modern humans arrived,” says Higham, perhaps in part because Europe was in the throes of an Ice Age at the time, so they were struggling against harsh conditions that couldn’t support large numbers of individuals. Modern humans, Higham observes, had been living in Africa, which was much more benign. “Modern humans also seemed to have more modern technology,” he says, “which wouldn’t have been a huge advantage, but over the long duration might have given them an edge.”

Scientists also know that Neanderthals and modern humans interbred at some level, which is why about 2% of our genes, on average, are Neanderthal in origin. The details of those interactions are still completely unknown—for now, anyway. “For me,” says Davies, “the big achievement here is that we now have a way of getting much more information out of both skeletal and archaeological remains. We can look at the molecular level on genetic inheritance, movement patterns, even what they were eating.”

The mystery of when and where the Neanderthals made their last stand may be just about wrapped up. And the answer to why they disappeared might not be a mystery for much longer.


TIME Culture

Study: Society Flourished When Humans Got Less Manly

A model of Peking man (Homo erectus pekinensis), who lived 1-2 million years ago Getty Images

Does lower T lead to higher tech? Research links decrease in manly traits to an increase in sophisticated toolmaking in early humans

Some anthropologists now believe that advanced human behaviors like toolmaking only developed when early humans evolved to have lower levels of testosterone than their ancestors, according to a new study published in Current Anthropology.

“All of a sudden, in the archeological record, culture and advanced technology suddenly becomes more widespread. And at that time we also see a decrease in testosterone,” said the study’s lead author Bob Cieri, a graduate student at the University of Utah. “Before 50,00 years ago, there were brief flashes of advanced behavior and artifacts, but they’re not persistent and widespread.”

Cieri measured the browridge of different human skulls, which indicates the level of testosterone in the skeleton. Heavier brows and longer faces indicate more testosterone, and more rounded heads indicate less testosterone, according to Stephen Churchill, the Duke professor who supervised Cieri’s work. Cieri measured 13 human skulls that were more than 80,000 years old; 41 skulls between 10,000 and 38,000 years old; and over 1,200 20th-century skulls from different ethnic populations. He found that the modern skulls had substantially more rounded features and less heavy brows than the early skulls, indicating a drop in testosterone between our early ancestors and modern humans.

Cieri says the decrease in testosterone levels could be attributed to the rise in the Homo sapiens population, which meant that people had to be nicer to each other because they were living in closer quarters. “If population density starts increasing, not only are there more people in your immediate environment that you have to get along with, but all land would be occupied with human groups,” he explains. “You wouldn’t just go across to the other side of the valley to hunt bison by yourself, you’d go to the other side of the valley and maybe make a treaty with the other people who live there.”

It’s important to note that these early humans didn’t yet have “culture” as we know it — they were still hunter-gatherers, Cieri says, but they were much less aggressive about it. But he thinks this lowering of testosterone led to more cooperation between people, which laid crucial groundwork for cultural advances thousands of years later.

So if you’re still worried about low T after reading TIME’s recent cover story, “Manopause?!,” consider that a little less T isn’t always a bad thing.

TIME Paleontology

Want to See a Live Dinosaur? Set Up a Bird Feeder

An exciting new study lays out in detail how our fine feathered friends evolved from the same ancestors as the T. Rex and velociraptors over the course of millions of years, and how they managed to avoid the same doomed fate as their dinosaur cousins

When the theory first arose that birds evolved directly from dinosaurs, it was enormously controversial. It was even more contentious when some paleontologists argued that birds are dinosaurs—the only branch of the family that survived a cataclysmic asteroid strike 65 million years ago.

That initial controversy has largely vanished, thanks to a series of astonishing discoveries over the past 20 years or so—for example, that many dinosaur species sported feathers, and that the bone structures of birds and dinos are similar in all sorts of ways. “We now know birds are a subgroup of dinosaurs, like humans are a subgroup of apes,” says paleontologist Michael Lee, of the South Australian Museum, in Adelaide.

Now a new report in Science by Lee and several colleagues has laid out in unprecedented detail the exact bird branch of the dinosaur tree that sprouted and evolved over some 50 million years—and how that evolution may have saved birds from extinction when the asteroid struck.

The study is based on a cross-species analysis of more than 1,500 anatomical features across 120 species of early birds and therapod dinosaurs—the branch that includes velociraptors and T. Rex, and which is most closely related to birds. Of all the evolutionary changes that reshaped the bird lineage, says Michael Benton, a paleontologist at the University of Bristol in the UK, writing in a commentary on the new paper that also appears in Science, “The key seems to be miniaturization.”

Starting about 200 million years ago, the paper shows, one group of therapods began to shrink rapidly, from an average weight of more than 350 lb. to less than two. Not only that, says Lee, but, “It turns out that birds and their direct ancestors evolved about four times faster than other dinosaurs over that time.”

It’s not unusual to see different rates of evolution in related species, he says. “Rodents are the most successful mammals by far, for example,” Lee says, “and one reason is that they have the most rapidly evolving DNA.” Rapid evolution could be one reason there are now 10,000 species of birds, but only a few dozen species of crocodiles, even though both are equally ancient.

Shrinkage isn’t the only change that transformed therapods into birds, says Benton. “There was miniaturization, but also modifications to the eyes, the elaboration of feathers, the development of wings out of the small, silly-looking forelimbs therapods have.”

These changes might have been driven by their helpfulness in letting birds adapt to living in trees—previously uninhabited ecological niche. It’s still just a hypothesis, says Benton, but “there might have been an opportunity to conquer a new habitat by getting smaller, developing the ability to climb and to glide, developing better vision so you don’t go banging into branches.”

The changes could also have given birds a huge advantage over other dinosaurs when the asteroid finally struck. “Birds obviously didn’t evolve knowing in advance that it would hit,” says Lee, “but the adaptations might have incidentally helped them survive—they could warm themselves with feathers [when dust from the asteroid cooled the Earth], fly long distances for food.”

What most people don’t realize, says Lee, is that birds didn’t show up just as the other dinosaurs were dying out. “They shared the world for 100 million years.” The quintessential proto-bird, Archaeopteryx, lived 150 million years ago, he points out. But the terrifying T. Rex wouldn’t show up until many tens of millions of years later.


TIME Friendship

Study: BFFs May Have Similar DNA

RyanJLane—Getty Images

Really close friends might be as genetically similar as fourth cousins

Next time someone says “You would really like my friend, she’s just like you,” try to refrain from giving her the side eye. It turns out she might have some science to back her up. According to a new study from Yale University and the University of California at San Diego, good friends are often genetically similar, and can share as much as 1% of the same gene variants. In genetic terms, that’s a lot. As close as, say, fourth cousins.

“This gives us a deeper accounting of the origins of friendship,” says Nicholas Christakis, professor of sociology, evolutionary biology, and medicine at Yale, who co-authored the study with James Fowler, professor of medical genetics and political science at UC San Diego. “Not only do we form ties with people superficially like ourselves, we form ties with people who are like us on a deep genetic level. They’re like our kin, though they’re not.”

To do their study, which was published in July in the Proceedings of the National Academy of Sciences, Christakis and Fowler looked at 1.5 million gene variants from the Framingham Heart Study, a dataset which has details on the friendships and genetics of its participants. Most of the participants were of European descent. Researchers genetically compared pairs of friends with pairs of strangers from among the same 1,932 subjects they studied. None of the pairs were related to each other.

The study found that, oddly, close friends are often genetically similar in their sense of smell. But it also concluded that friendship may play a role in evolution. The genes that were shared by friends saw the most “evolutionary activity”, or have evolved the fastest over the past 30,000 years. Whether the friendship or the genetic similarity came first is up for debate. Do we seek out genetically similar friends or do our friendships and mating affect what genes get passed on

“Human beings are one of the few species who form long-term, non-reproductive relationships with other members of our species,” says Fowler. “This role of affiliation is important. It ties into the success of our species.”

TIME behavior

These Goosebump Sensors Can Read Your Emotions

The Goose Bump Detector is a goose bump monitoring sensor attached to the arm. Young-Ho Cho/KAIST

Sounds crazy right? Read on

South Korean researchers are developing a technology that can measure your goosebumps—which are activated when you’re cold, sure, but also when you’re scared, moved or otherwise emotionally aroused. It sounds weird until you consider the potential applications for such a thing, some of which are fascinating while others seem unsettling when it comes to emotional privacy.

A team of scientists at KAIST in Daejeon, South Korea have developed a very thin sticker-like sensor that can easily be applied to the skin. The wearable 20mm x 20mm polymer sensor measures goosebumps, and the researchers believe it provides insight into human’s emotional states.

Although the sensors are still in early development, the team believes they could provide insight into physical and emotional responses so that they can determine how people experience and react to the world around them. This could help lead the way to personalized music streams and advertising, the researchers suggest in a statement. “In the future, human emotions will be regarded like any typical biometric information, including body temperature or blood pressure,” study author Young-Ho Cho said.

Social media sites like Facebook are already tapping into what the site perceives as your interests in order to curate advertising targeted just for you. Analyzing your emotions would take that kind of monitoring to a whole new level. Emotion sensing is something retailers are interested in, and companies like 3VR are rolling out initiatives like “big data video-mining,” which uses video cameras that can estimate the age, gender, and mood shoppers as they pass through a given store.

But what can goosebumps tell us? The obvious reason we get goosebumps is that it’s a biological method to combat chills. Goosebumps occur when tiny muscles attached to each of our hairs contract, and the areas surrounding that contraction rises. In animals with a lot of fur, this retains heat. We don’t have a lot of fur, so it doesn’t exactly serve the same purpose for us—but it does clue us into when our bodies are at an uncomfortable level.

When it comes to getting goosebumps while watching a sad or inspiring movie, it’s a little more evolutionarily confusing, but researchers think it’s because we release the stress hormone adrenaline when we feel strong emotions, and that hormone can trigger goosebumps to rise. “This response is an evolutionary holdover from our primate ancestors. Those ancestors had long hair that stood out when those tiny muscles contracted, making the individual look larger and usually more fierce when something threatening or scary occurred,” says Dr. Rick Potts, director of the human origins program at the Smithsonian Institution. “There was an evolutionary advantage for our ancestors, but for us, the advantage has disappeared—though we retain the impulse of those tiny muscles contracting just beneath the skin.”

The research is published in the journal Applied Physics Letters and it’s still preliminary. But knowing there’s a market for understanding your emotions is enough to give us goosebumps.

TIME Science

Diving Beetles Could One Day Help Scuba Divers

A large Diving Beetle plunges into the water. Barrett & MacKay—Getty Images/All Canada Photos

It's all about the suction-cup pads on the male beetle's legs

Male diving beetles have adhesive plungers on their forelegs that allow them to hold onto their female mating partners, a recent study published in Journal of the Royal Society Interface reports. And the effectiveness of those plungers could point ways forward for the design of human underwater equipment.

The team of researchers from Taiwan saw that female underwater beetles in the dystiscidae family squirmed to avoid copulation with an undesirable suitor, triggering a need for the adaptation in the males’ legs.

The team of scientists, led by Dr Kai-Jung Chi from National Chung Hsing University, compared the gripping features of two species of male aquatic beetles — one that had spatula-shaped bristles and a more evolved diving beetle that had suction-cup-shaped pads. Researchers found that the primitive beetles released a glue-like secretion, but the beetles with the circular plungers on their legs were able to withstand seven times more force than the others — proving that the suction cup posed a sexual advantage.

Scientists hope that the success of the male aquatic beetles’ adhesive legs will help inspire innovations in aquatic equipment such as the attachments used by underwater rescuers or scuba divers.

TIME Research

We Evolved To Withstand Getting Punched in The Face

University of Utah
University of Utah An artist's impression of how human faces may have evolved to minimise injury from punches.

"When modern humans fight hand to hand, the face is usually the primary target," a researcher says

Humans evolved to minimize injury incurred by punches to the face, a new study suggests.

Researchers at the University of Utah observed that the fossils of australopiths—bi-peds that lived 4-5 million years ago and directly preceded the human genus Homo—had robust cheek, jaw, eye and nose features. Scientists had previously thought that the australopiths’ strong facial features were an evolutionary adaptation to their hardy diet, but the study published in the journal Biological Reviews suggests that they were likely eating softer foods like fruit.

Dr. David Carrier, the lead researcher in the study, told the Guardian that the australopiths’ hands had adapted to form a fist, allowing them to engage in hand-to-hand combat. “When modern humans fight hand to hand, the face is usually the primary target,” Carrier said. Carrier and his team found that the bones that had evolved to be more robust were typically the features that suffer the greatest impact in a fight.

The study also shows that while the faces, hands and up-right nature of australopiths evolved to allow for improved fighting, modern-day humans have less robust facial features. Carrier told BBC that humans have less of a need to protect themselves because violence is no longer a driving evolutionary factor. “There’s a temporal correlation,” Carrier said.

TIME Religion

The Economy Is More Important Than Fighting Over Evolution

An evolutionist went fly-fishing with Tea Partiers, and they had more in common than she thought.

Last week, the New York Times reported that yet another Christian school—this time Tennessee’s Bryan College—is embroiled in a debate about the instruction of evolution on its campus. As a theologian, pastor, and seminary president I believe in evolution, and we certainly don’t teach creationism here at Union Theological Seminary. I also know that for this and many other issues you can’t just go to the Bible and find a passage that tells you exactly what to think.

However, reading the article left me feeling confused. Why, almost a century after the Scopes trial, are Christians still fighting about evolution—an issue wholly unrelated to Jesus’ gospel charge—while ignoring the egregious sin of systemic wealth inequality? When it comes to economic justice and the abolition of poverty, you don’t need any interpretive tools to approach the Christian Scriptures. Each page in our Holy Book addresses economic realities and makes clear to those gathered under the gracious arms of God what kind of world we should seek: a world where there is no poverty. It is not ambiguous.

Since I was three years-old, my family and I have jigsawed ourselves into the proverbial station wagon every summer and driven into the wilderness for three weeks of fly fishing. This past summer, I couldn’t find anyone who would agree to go along, and—mostly because I needed the kind of soul renewal that comes with it—I decided I was going to do it by myself. I signed up to go twenty miles into the Bob Marshall Wilderness on horseback with a group of people I didn’t know to fly fish for 10 days. We were an amazing, offbeat coterie and we got to know each other really well, really quickly. It wasn’t until the third day that I accidentally found out that everyone in the group was a member of the Tea Party.

There was great laughter when everyone realized that I had discovered it. They confessed that they quickly realized I was a liberal Yankee. What struck me most about our conversations around issues of economics was that the language and concerns that were spoken did not, on the whole, sound very different at all from those that I hear from my students here at Union, one of the most socially and politically progressive seminaries in the country. During Occupy Wall Street, 62 students went down from Union to Zuccotti Park, set up their tents, built their camp fires, and lived there for three months to bear witness to their desire for a new economic reality.

Among my new Tea Party friends and my long-beloved students, I heard three things passionately echo over and over again, with little discrepancy.

First, there is a shared conviction that the economic system in which we presently live is completely corrupt, and that Wall Street and the leaders of corporate America are not concerned about the flourishing of common people.

Second, there is a deep concern about the failure of our political system to work on behalf of the United States citizenry. Both Tea Partiers and Occupiers demand a government that is truly of the people, not one that merely masquerades as such.

Third, there is an anxiety about the destruction of the values of community—the values that mark how we care for our children; how we decide what we eat; how we build homes for ourselves; and how we constitute communities where we feel safe.

I travel with a flyer in my pocket that I was able to pull out several more days into the trip and share with them. It’s called the Freedom Budget for All Americans, drafted in 1966 by the A. Philip Randolph Institute in Atlanta under the leadership of Reverend Dr. Martin Luther King, Jr. and Bayard Rustin. This manifesto for economic change reminds me of the work ahead.

“We are budgeting our resources,” it says, “so that our nation can achieve freedom from want.” It’s not a complicated socialist or communist vision: guaranteed full employment, full production and high economic growth, an adequate minimum wage, farm income parity, guaranteed income for all who are unable to work, a decent home for every American family, modern health services for all, full educational opportunities for all, updated social security and welfare programs, equitable tax and money policies. It’s a Christian vision of economic justice in which people thrive because their basic human needs are met.

It is startling that fifty years later we have not—on a national level—taken steps toward the realization of any of these desires. In fact, in some areas, we’ve moved backwards. We must be better.

Perhaps what we need are more fly fishing moments, where our perceptions are challenged and we glimpse the possibility of a movement. Anything less than the abolition of poverty is too costly.

Serene Jones is President of Union Theological Seminary in the City of New York where she holds the Johnston Family Chair in Religion and Democracy. She is Vice President of the American Academy of Religion, an ordained minister in the United Church of Christ and the Christian Church (Disciples of Christ), and author of Trauma and Grace: Theology in a Ruptured World. This piece is adapted from one of her recent sermons, preached at Trinity Episcopal Cathedral in Cleveland. She tweets online at @SereneJones.

TIME review

We Are All Fish

Part of the family: Shubin and a model of the Tiktaalik—ancestor to us all
Part of the family: Shubin and a model of the Tiktaalik—ancestor to us all Chicago Tribune; MCT via Getty Images

Like it or not, your genes run all the way back to a fishy critter called Tiktaalik that led the way to land 375 million years ago. A new documentary shows why the ancient animal deserves an honored spot in your family tree

Anti-evolutionists have at least one thing in common with climate-change deniers and anti-vaccine nuts: they keep repeating nonsense long after it’s been debunked, and if you debunk it one more time, they pretend they can’t hear you and just keep going. Lather, rinse, repeat—it just never ends.

One of the evolution-haters’ favorites, for example, is this: if evolution really happened, with one species giving rise to another, why aren’t there any transitional fossils? Put that in your pipe and smoke it, Professor Darwin.

It would be a devastating critique if true, but it’s hogwash. Our relatively recent ancestor Lucy had both apelike and human characteristics, and paleontologists have found many more examples going back hundreds of millions of years. One of the most dramatic was announced in 2006: an ancient fishlike creature dubbed Tiktaalik. Dating back some 375 million years, it had gills, scales and a mostly fishy body. But its fins concealed bones and joints of a type never before seen in a fish, which let it crawl around on land. It was either our great-great-great (repeat many times) grandfish. Or at least, it was related.

Neil Shubin, the University of Chicago scientist who led the team that dug up Tiktaalik, went on to write a best-selling book about it, titled Your Inner Fish. That led to a three-part PBS series, and now that series is available on DVD. It’s well worth watching.

Part of the reason Your Inner Fish deserves your now fully human attention is that Shubin is such an engaging guide to what could otherwise be a dry and dusty topic, but which, thanks to his genial enthusiasm and clarity, is anything but. The search for Tiktaalik was a scientific detective story, and that’s just how he lays it out. Fish, he reminds us, were the first animals with backbones, skulls and overall bony skeletons. They swam the world’s oceans 400 million years ago—and then, 40 million years later, the first amphibians were up on land.

Something must have happened in that 40-million year gap to make the transition to land possible, and armed with the knowledge of the timeframe and the places in the world where sedimentary rock of the right age was accessible, Shubin and his team ended up on Ellesmere Island, in spectacularly remote and austere landscape not far from the northern tip of Greenland. It took years of painstaking searching, requiring return visits during the brief Arctic summer year after year for a full decade until, in the second week of July, 2004, they found what they were looking for.

“I worked that site for ten years,” Shubin told TIME, “so making the documentary was like a homecoming. Being there again, telling the story to a fresh audience right at that wonderful, magical place was just wonderful.” Equally wonderful is the bombproof logic of what they found and what it meant. Darwin said such a creature must exist; previously known fossils dictated when it must have lived; and sure enough, there it was. That’s about as solid a demonstration of the scientific method in action as you could imagine.

The series is about more than just the search for Tiktaalik: parts 2 and 3 are titled Your Inner Reptile and Your Inner Monkey. Just as part 1 illustrates the legacy we still carry from our fishlike ancestors, the second and third installments reveal what we inherited from reptiles (our skin, teeth and ears in particular) and what we got from ancestral primates (hands, vision, brains, along with some less desirable traits such as weak backs and a poor sense of smell).

It’s a fascinating journey, and Shubin introduces us along the way to some of the giants in modern paleontology—his counterparts in the search for crucial transitional creatures, and his own scientific heroes. “To stand at the Lucy site with Don Johanson and to be out in the field with Tim White,” he says, “was a real privilege.”

At no point in the series does Shubin get preachy about why you really, really ought to accept evolution. It’s enough for him to demonstrate, in a captivating and powerful way, and for the millionth time, that evolution is the only conceivable explanation for the spectacular variety of species on Earth—or that, as Darwin put it, “….from so simple a beginning endless forms most beautiful and most wonderful have been, and are being, evolved.” It’s not the only explanation, of course.

It’s possible that God created the world 6,000 years ago and buried vast number of fossils that simply seem to be millions of years old, with a progression of forms that seem to prove Darwin’s theory over and over and over again. Seems like an awful waste of time, though.

TIME The Weekend Read

What Science Says About Race and Genetics

Illustration by Umberto Mischi for TIME

The New York Times' former science editor on research showing that evolution didn't stop when human history began.

A longstanding orthodoxy among social scientists holds that human races are a social construct and have no biological basis. A related assumption is that human evolution halted in the distant past, so long ago that evolutionary explanations need never be considered by historians or economists.

New analyses of the human genome have established that human evolution has been recent, copious, and regional.In the decade since the decoding of the human genome, a growing wealth of data has made clear that these two positions, never at all likely to begin with, are simply incorrect. There is indeed a biological basis for race. And it is now beyond doubt that human evolution is a continuous process that has proceeded vigorously within the last 30,000 years and almost certainly — though very recent evolution is hard to measure — throughout the historical period and up until the present day.

New analyses of the human genome have established that human evolution has been recent, copious, and regional. Biologists scanning the genome for evidence of natural selection have detected signals of many genes that have been favored by natural selection in the recent evolutionary past. No less than 14% of the human genome, according to one estimate, has changed under this recent evolutionary pressure.

Analysis of genomes from around the world establishes that there is a biological basis for race, despite the official statements to the contrary of leading social science organizations. An illustration of the point is the fact that with mixed race populations, such as African Americans, geneticists can now track along an individual’s genome, and assign each segment to an African or European ancestor, an exercise that would be impossible if race did not have some basis in biological reality.

Racism and discrimination are wrong as a matter of principle, not of science. That said, it is hard to see anything in the new understanding of race that gives ammunition to racists. The reverse is the case. Exploration of the genome has shown that all humans, whatever their race, share the same set of genes. Each gene exists in a variety of alternative forms known as alleles, so one might suppose that races have distinguishing alleles, but even this is not the case. A few alleles have highly skewed distributions but these do not suffice to explain the difference between races. The difference between races seems to rest on the subtle matter of relative allele frequencies. The overwhelming verdict of the genome is to declare the basic unity of humankind.

Genetics and Social Behavior

Human evolution has not only been recent and extensive, it has also been regional. The period of 30,000 to 5,000 years ago, from which signals of recent natural selection can be detected, occurred after the splitting of the three major races, so represents selection that has occurred largely independently within each race. The three principal races are Africans (those who live south of the Sahara), East Asians (Chinese, Japanese, and Koreans), and Caucasians (Europeans and the peoples of the Near East and the Indian subcontinent). In each of these races, a different set of genes has been changed by natural selection. This is just what would be expected for populations that had to adapt to different challenges on each continent. The genes specially affected by natural selection control not only expected traits like skin color and nutritional metabolism, but also some aspects of brain function. Though the role of these selected brain genes is not yet understood, the obvious truth is that genes affecting the brain are just as much subject to natural selection as any other category of gene.

Human social structures change so slowly and with such difficulty as to suggest an evolutionary influence at work.What might be the role of these brain genes favored by natural selection? Edward O. Wilson was pilloried for saying in his 1975 book Sociobiology that humans have many social instincts. But subsequent research has confirmed the idea that we are inherently sociable. From our earliest years we want to belong to a group, conform to its rules and punish those who violate them. Later, our instincts prompt us to make moral judgments and to defend our group, even at the sacrifice of one’s own life.

Anything that has a genetic basis, such as these social instincts, can be varied by natural selection. The power of modifying social instincts is most visible in the case of ants, the organisms that, along with humans, occupy the two pinnacles of social behavior. Sociality is rare in nature because to make a society work individuals must moderate their powerful selfish instincts and become at least partly altruistic. But once a social species has come into being, it can rapidly exploit and occupy new niches just by making minor adjustments in social behavior. Thus both ants and humans have conquered the world, though fortunately at different scales.

Conventionally, these social differences are attributed solely to culture. But if that’s so, why is it apparently so hard for tribal societies like Iraq or Afghanistan to change their culture and operate like modern states? The explanation could be that tribal behavior has a genetic basis. It’s already known that a genetic system, based on the hormone oxytocin, seems to modulate the degree of in-group trust, and this is one way that natural selection could ratchet the degree of tribal behavior up or down.

Human social structures change so slowly and with such difficulty as to suggest an evolutionary influence at work. Modern humans lived for 185,000 years as hunters and gatherers before settling down in fixed communities. Putting a roof over one’s head and being able to own more than one could carry might seem an obvious move. The fact that it took so long suggests that a genetic change in human social behavior was required and took many generations to evolve.

Tribalism seems to be the default mode of human political organization. It can be highly effective: The world’s largest land empire, that of the Mongols, was a tribal organization. But tribalism is hard to abandon, again suggesting that an evolutionary change may be required.

The various races have evolved along substantially parallel paths, but because they have done so independently, it’s not surprising that they have made these two pivotal transitions in social structure at somewhat different times. Caucasians were the first to establish settled communities, some 15,000 years ago, followed by East Asians and Africans. China, which developed the first modern state, shed tribalism two millennia ago, Europe did so only a thousand years ago, and populations in the Middle East and Africa are in the throes of the process.

Two case studies, one from the Industrial Revolution and the other from the cognitive achievements of Jews, provide further evidence of evolution’s hand in shaping human social behavior within the recent past.

The Behavioral Makeover Behind the Industrial Revolution

The essence of the Industrial Revolution was a quantum leap in society’s productivity. Until then, almost everyone but the nobility lived a notch or two above starvation. This subsistence-level existence was a characteristic of agrarian economies, probably from the time that agriculture was first invented.

Perhaps productivity increased because the nature of the people had changed.The reason for the economic stagnation was not lack of inventiveness: England of 1700 possessed sailing ships, firearms, printing presses, and whole suites of technologies undreamed of by hunter gatherers. But these technologies did not translate into better living standards for the average person. The reason was a Catch-22 of agrarian economies, called the Malthusian trap, after the Rev. Thomas Malthus. In his 1798 Essay on the Principle of Population, Malthus observed that each time productivity improved and food became more plentiful, more infants survived to maturity, and the extra mouths ate up the surplus. Within a generation, everyone was back to living just above starvation level.

Malthus, strangely enough, wrote his essay at the very moment when England, shortly followed by other European countries, was about to escape from the Malthusian trap. The escape consisted of such a substantial increase in production efficiency that extra workers enhanced incomes instead of constraining them.

This development, known as the Industrial Revolution, is the salient event in economic history, yet economic historians say they have reached no agreement on how to account for it. “Much of modern social science originated in efforts by late nineteenth and twentieth century Europeans to understand what made the economic development path of western Europe unique; yet these efforts have yielded no consensus,” writes the historian Kenneth Pomeranz. Some experts argue that demography was the real driver: Europeans escaped the Malthusian trap by restraining fertility through methods such as late marriage. Others cite institutional changes, such as the beginnings of modern English democracy, secure property rights, the development of competitive markets, or patents that stimulated invention. Yet others point to the growth of knowledge starting from the Enlightenment of the 17th and 18th century or the easy availability of capital.

This plethora of explanations and the fact that none of them is satisfying to all experts point strongly to the need for an entirely new category of explanation. The economic historian Gregory Clark has provided one by daring to look at a plausible yet unexamined possibility: that productivity increased because the nature of the people had changed.

Clark’s proposal is a challenge to conventional thinking because economists tend to treat people everywhere as identical, interchangeable units. A few economists have recognized the implausibility of this position and have begun to ask if the nature of the humble human units that produce and consume all of an economy’s goods and services might possibly have some bearing on its performance. They have discussed human quality, but by this they usually mean just education and training. Others have suggested that culture might explain why some economies perform very differently from others, but without specifying what aspects of culture they have in mind. None has dared say that culture might include an evolutionary change in behavior — but neither do they explicitly exclude this possibility.

To appreciate the background of Clark’s idea, one has to return to Malthus. Malthus’s essay had a profound effect on Charles Darwin. It was from Malthus that Darwin derived the principle of natural selection, the central mechanism in his theory of evolution. If people were struggling on the edge of starvation, competing to survive, then the slightest advantage would be decisive, Darwin realized, and the owner would bequeath that advantage to his children. These children and their offspring would thrive while others perished.

“In October 1838, that is, fifteen months after I had begun my systematic inquiry,” Darwin wrote in his autobiography, “I happened to read for amusement Malthus on Population, and being well prepared to appreciate the struggle for existence which everywhere goes on from long-continued observation of the habits of animals and plants, it at once struck me that under these circumstances favorable variations would tend to be preserved, and unfavorable ones to be destroyed. The results of this would be the formation of a new species. Here then I had at last got a theory by which to work.”

Given the correctness of Darwin’s theory, there is no reason to doubt that natural selection was working on the very English population that provided the evidence for it. The question is that of just what traits were being selected for.

The Four Key Traits

Clark has documented four behaviors that steadily changed in the English population between 1200 and 1800, as well as a highly plausible mechanism of change. The four behaviors are those of interpersonal violence, literacy, the propensity to save, and the propensity to work.

Profound events are likely to have profound causes.Homicide rates for males, for instance, declined from 0.3 per thousand in 1200 to 0.1 in 1600 and to about a tenth of this in 1800. Even from the beginning of this period, the level of personal violence was well below that of modern hunter-gatherer societies. Rates of 15 murders per thousand men have been recorded for the Aché people of Paraguay.

Work hours steadily increased throughout the period, and interest rates fell. When inflation and risk are subtracted, an interest rate reflects the compensation that a person will demand to postpone immediate gratification by postponing consumption of a good from now until a future date. Economists call this attitude time preference, and psychologists call it delayed gratification. Children, who are generally not so good at delaying gratification, are said to have a high time preference. In his celebrated marshmallow test, the psychologist Walter Mischel tested young children as to their preference for receiving one marshmallow now or two in fifteen minutes. This simple decision turned out to have far-reaching consequences: Those able to hold out for the larger reward had higher SAT scores and social competence in later life. Children have a very high time preference, which falls as they grow older and develop more self-control. American six-year-olds, for instance, have a time preference of about 3% per day, or 150% per month; this is the extra reward they must be offered to delay instant gratification. Time preferences are also high among hunter-gatherers.

Interest rates, which reflect a society’s time preferences, have been very high — about 10% — from the earliest historical times and for all societies before 1400 AD for which there is data. Interest rates then entered a period of steady decline, reaching about 3% by 1850. Because inflation and other pressures on interest rates were largely absent, Clark argues, the falling interest rates indicate that people were becoming less impulsive, more patient, and more willing to save.

These behavioral changes in the English population between 1200 and 1800 were of pivotal economic importance. They gradually transformed a violent and undisciplined peasant population into an efficient and productive workforce. Turning up punctually for work every day and enduring eight eight hours or more of repetitive labor is far from being a natural human behavior. Hunter-gatherers do not willingly embrace such occupations, but agrarian societies from their beginning demanded the discipline to labor in the fields and to plant and harvest at the correct times. Disciplined behaviors were probably evolving gradually within the agrarian English population for many centuries before 1200, the point at which they can be documented.

Clark has uncovered a genetic mechanism through which the Malthusian economy may have wrought these changes on the English population: The rich had more surviving children than did the poor. From a study of wills made between 1585 and 1638, he finds that will makers with £9 or less to leave their heirs had, on average, just under two children. The number of heirs rose steadily with assets, such that men with more than £1,000 in their gift, who formed the wealthiest asset class, left just over four children.

The English population was fairly stable in size from 1200 to 1760, meaning that if the rich were having more children than the poor, most children of the rich had to sink in the social scale, given that there were too many of them to remain in the upper class.

Their social descent had the far-reaching genetic consequence that they carried with them inheritance for the same behaviors that had made their parents rich. The values of the upper middle class — nonviolence, literacy, thrift, and patience — were thus infused into lower economic classes and throughout society. Generation after generation, they gradually became the values of the society as a whole. This explains the steady decrease in violence and increase in literacy that Clark has documented for the English population. Moreover, the behaviors emerged gradually over several centuries, a time course more typical of an evolutionary change than a cultural change.

In a broader sense, these changes in behavior were just some of many that occurred as the English population adapted to a market economy. Markets required prices and symbols and rewarded literacy, numeracy, and those who could think in symbolic ways. “The characteristics of the population were changing through Darwinian selection,” Clark writes. “England found itself in the vanguard because of its long, peaceful history stretching back to at least 1200 and probably long before. Middle-class culture spread throughout the society through biological mechanisms.”

Economic historians tend to see the Industrial Revolution as a relatively sudden event and their task as being to uncover the historical conditions that precipitated this immense transformation of economic life. But profound events are likely to have profound causes. The Industrial Revolution was caused not by events of the previous century but by changes in human economic behavior that had been slowly evolving in agrarian societies for the previous 10,000 years.

This of course explains why the practices of the Industrial Revolution were adopted so easily by other European countries, the United States, and East Asia, all of whose populations had been living in agrarian economies and evolving for thousands of years under the same harsh constraints of the Malthusian regime. No single resource or institutional change — the usual suspects in most theories of the Industrial Revolution — is likely to have become effective in all these countries around 1760, and indeed none did.

That leaves the questions of why the Industrial Revolution was perceived as sudden and why it emerged first in England instead of in any of the many other countries where conditions were ripe. Clark’s answer to both these questions lies in the sudden growth spurt in the English population, which tripled between 1770 and 1860. It was this alarming expansion that led Malthus to write his foreboding essay on population.

But contrary to Malthus’s gloomy prediction of a population crash induced by vice and famine, which would have been true at any earlier stage of history, incomes on this occasion rose, heralding the first escape of an economy from the Malthusian trap. English workmen contributed to this spurt, Clark dryly notes, as much by their labors in the bedroom as on the factory floor.

Clark’s data provide substantial evidence that the English population responded genetically to the harsh stresses of a Malthusian regime and that the shifts in its social behavior from 1200 to 1800 were shaped by natural selection. The burden of proof is surely shifted to those who might wish to assert that the English population was miraculously exempt from the very forces of natural selection whose existence it had suggested to Darwin.

Explaining Ashkenazi IQ

A second instance of very recent human evolution may well be in evidence in European Jews, particularly the Ashkenazim of northern and central Europe. In proportion to their population, Jews have made outsize contributions to Western civilization. A simple metric is that of Nobel prizes: Though Jews constitute only 0.2% of the world’s population, they won 14% of Nobel prizes in the first half of the 20th century, 29% in the second and so far 32% in the present century. There is something here that requires explanation. If Jewish success were purely cultural, such as hectoring mothers or a zeal for education, others should have been able to do as well by copying such cultural practices. It’s therefore reasonable to ask if genetic pressures in Jews’ special history may have enhanced their cognitive skills.

It’s reasonable to ask if genetic pressures in Jews’ special history may have enhanced their cognitive skills.Just such a pressure is described by two economic historians, Maristella Botticini and Zvi Eckstein, in their book “The Chosen Few.” In 63 or 65 AD, the high priest Joshua ben Gamla decreed that every Jewish father should send his sons to school so that they could read and understand Jewish law. Jews at that time earned their living mostly by farming, as did everyone else, and education was both expensive and of little practical use. Many Jews abandoned Judaism for the new and less rigorous Jewish sect now known as Christianity.

Botticini and Eckstein say nothing about genetics but evidently, if generation after generation the Jews less able to acquire literacy became Christians, literacy and related abilities would on average be enhanced among those who remained Jews.

As commerce started to pick up in medieval Europe, Jews as a community turned out to be ideally suited for the role of becoming Europe’s traders and money-lenders. In a world where most people were illiterate, Jews could read contracts, keep accounts, appraise collateral, and do business arithmetic. They formed a natural trading network through their co-religionists in other cities, and they had rabbinical courts to settle disputes. Jews moved into money-lending not because they were forced to do so, as some accounts suggest, but because they chose the profession, Botticini and Eckstein say. It was risky but highly profitable. The more able Jews thrived and, just as in the rest of the pre-19th century world, the richer were able to support more surviving children.

As Jews adapted to a cognitively demanding niche, their abilities increased to the point that the average IQ of Ashkenazi Jews is, at 110 to 115, the highest of any known ethnic group. The population geneticists Henry Harpending and Gregory Cochran have calculated that, assuming a high heritability of intelligence, Ashkenazi IQ could have risen by 15 points in just 500 years. Ashkenazi Jews first appear in Europe around 900 AD, and Jewish cognitive skills may have been increasing well before then.

The emergence of high cognitive ability among the Ashkenazim, if genetically based, is of interest both in itself and as an instance of natural selection shaping a population within the very recent past.

The Adaptive Response to Different Societies

The hand of evolution seems visible in the major transitions in human social structure and in the two case studies described above. This is of course a hypothesis; proof awaits detection of the genes in question. If significant evolutionary changes can occur so recently in history, other major historical events may have evolutionary components. One candidate is the rise of the West, which was prompted by a remarkable expansion of European societies, both in knowledge and geographical sway, while the two other major powers of the medieval world, China and the house of Islam, ascendant until around 1500 AD, were rapidly overtaken.

Civilizations may rise and fall but evolution never ceases.In his book The Wealth and Poverty of Nations, the economic historian David Landes examines every possible factor for explaining the rise of the West and the stagnation of China and concludes, in essence, that the answer lies in the nature of the people. Landes attributes the decisive factor to culture, but describes culture in such a way as to imply race.

“If we learn anything from the history of economic development, it is that culture makes all the difference,” he writes. “Witness the enterprise of expatriate minorities — the Chinese in East and Southeast Asia, Indians in East Africa, Lebanese in West Africa, Jews and Calvinists throughout much of Europe, and on and on. Yet culture, in the sense of the inner values and attitudes that guide a population, frightens scholars. It has a sulfuric odor of race and inheritance, an air of immutability.”

Sulfuric odor or not, the culture of each race is what Landes suggests has made the difference in economic development. The data gathered by Clark on declining rates of violence and increasing rates of literacy from 1200 to 1800 provide some evidence for a genetic component to culture and social institutions.

Though equivalent data does not exist for the Chinese population, China’s society has been distinctive for at least 2,000 years and intense pressures on survival would have adapted the Chinese to their society just as Europeans became adapted to theirs.

Do Chinese carry genes for conformism and authoritarian rule? May Europeans have alleles that favor open societies and the rule of law? Obviously this is unlikely to be the case. But there is almost certainly a genetic component to the propensity for following society’s rules and punishing those who violate them. If Europeans were slightly less inclined to punish violators and Chinese slightly more so, that could explain why European societies are more tolerant of dissenters and innovators, and Chinese societies less so. Because the genes that govern rule following and punishment of violators have not yet been identified, it is not yet known if these do in fact vary in European and Chinese populations in the way suggested. Nature has many dials to twist in setting the intensities of the various human social behaviors and many different ways of arriving at the same solution.

For most of recorded history, Chinese civilization has been pre-eminent and it’s reasonable to assume that the excellence of Chinese institutions rests on a mix of culture and inherited social behavior.

The rise of the West, too, is unlikely to have been just some cultural accident. As European populations became adapted to the geographic and military conditions of their particular ecological habitat, they produced societies that have turned out to be more innovative and productive than others, at least under present circumstances.

That does not of course mean that Europeans are superior to others — a meaningless term in any case from the evolutionary perspective – any more than Chinese were superior to others during their heyday. China’s more authoritarian society may once again prove more successful, particularly in the wake of some severe environmental stress.

Civilizations may rise and fall but evolution never ceases, which is why genetics may play some role alongside the mighty force of culture in shaping the nature of human societies. History and evolution are not separate processes, with human evolution grinding to a halt some decent interval before history begins. The more that we are able to peer into the human genome, the more it seems that the two processes are delicately intertwined.

Nicholas Wade is a former science editor at The New York Times. This piece is adapted from the new book, A Troublesome Inheritance, published by the Penguin Press.

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