Society Man

In a provocative new study, MU’s David Geary argues that social competition powered the brain’s evolution.

Would Darwin Have Been a Fan of Reality TV?

Maybe so. Just consider what goes on during a show like Survivor: contestants’ skills and personalities are sized up. Alliances form. Plots are hatched. Tribes compete. There are winners; there are losers. There are survivors.

We might not automatically think of the winners of these shows as the fittest specimens of humanity. But it was the struggle for social dominance — something like Survivor-style competition — that powered the evolution of the human brain.

That’s the provocative theory drawn from a new analysis by University of Missouri psychologist David Geary and his graduate student Drew Bailey.

Geary, a Curators’ Professor in the Department of Psychological Sciences, is known internationally for his research into how children develop math skills. But it’s his other line of study, one that gives an evolutionary spin to psychological research, that has stirred controversy.

Neanderthal Man with glasses. Photo illustration by Blake Dinsdale. Reproduction of Neanderthal Man in Chicago Field Museum © Bettmann/Corbis

Critics of evolutionary psychology, such as the linguist Noam Chomsky, compare its theories to “just-so stories.” Any behaviors, they argue, can be described as successful evolutionary adaptations: Cooperation among individuals could have evolved because it contributes to perpetuating their genes; fighting could have evolved because it perpetuates one individual’s genes over someone else’s. Some of Geary’s colleagues in evolutionary psychology have held fast to the idea that our large brains are not the result of social competition, but of challenges related to environmental changes.

Geary has answered back by marshalling massive amounts of research to support his evolutionary explanations. His books on evolutionary psychology are widely considered among the definitive works in the field. But he’s faced tough criticism in the past for proposing Darwinian explanations for differences in the ways men and women behave. That has made him a widely quoted source when gender controversies erupt.

Geary’s latest research looks at why the brains of hominids, our upright-walking ancestors, grew larger and more sophisticated, tripling in size over the past two million years. His findings challenge the importance of some of the most accepted ideas. Yes, mastery of tool making, hunting and the use of fire all relied on growing brainpower. But brain evolution didn’t stop there, according to Geary. Social competition also favored the survival of the brainiest.

“Our ability to manipulate the environment set the stage for a within-the-species arms race,” Geary says. “When resources diminish, who gets the best resources: access to running water, the best fishing at the lake, the biggest piece of meat? What becomes important is social status.”

Getting ahead socially is all about politics. And politics takes intelligence to strategize.

“We’re all thinking ahead about how to get what we want,” Geary says. “If you can think two months ahead and everyone else can think just two weeks ahead, it’s not going to be hard to outwit them.”

That ability to plot many steps ahead is one of the key things that separates us from the apes. “Chimps don’t have a five-year plan; they don’t even have a five-week plan. Maybe five days, but we don’t know.”

Evolving progressively more brain matter may seem like an obvious advantage. But bigger brains come with serious costs, as well. Indeed, the human brain is an expensive organ in evolutionary terms: it consumes about 20 percent of our caloric intake. In a five-year-old, more than 40 percent of the calories consumed go to brain development and activity.

“When a population crashes, there seems to be an inverse relationship between social status and mortality. People get hungry, tensions rise, they become less egalitarian.”

“It’s a really interesting question,” Geary says. “There’s no reason for a brain to get bigger, necessarily. It’s not going to get bigger unless there’s a good reason.”

Many scientists suggest that the growth in hominid brain size was driven by the need to master the physical environment. Brainier individuals were better at hunting prey and gathering food. When our ancestors migrated out of central Africa, they faced more drastic changes in seasons and the wider range of temperatures and food shortages that go with them. Those with the intellect to build shelters, make clothing and store food for the winter were more likely to survive.

Cooler environments also meant fewer parasites, so the immune system made fewer metabolic demands. That may have freed up calories for bigger brains. Evidence supports these theories. For example, animals facing greater challenges foraging or finding prey have bigger brains than related species that have an easier time getting food.

Researchers who have studied the fossil records of hominids have also found that brains tend to be somewhat bigger farther from the equator. But Geary wasn’t thoroughly satisfied with these environmental explanations. “It didn’t seem like these climatic hypotheses were telling the full story,” he says.

For one, while some hominids stayed in central Africa and some migrated, they all were evolving larger brains at about the same rate. And much of the research supporting a climatic explanation correlated increasing brain size with just one variable such as latitude or average temperatures.

“When you have that situation you can have exaggerated effects because you haven’t controlled for (other) variables,” he says. “What we did differently was estimate all things simultaneously.”

Geary worked with Bailey to collect data on several variables. They took the estimated brain measurements of 175 hominid skulls that had been discovered over the years and plotted their locations by latitude -- from central Africa to as far afield as Indonesia -- and their ages, from 1.9 million to 10,000 years old.

Then Geary and Bailey considered how brain sizes varied by the prevalence of harmful parasites in the region, the average annual temperature and how much temperatures varied. They also looked at population density by counting how many skulls were found in a given area.

In an article published in January in the journal Human Nature, Geary and Bailey reported that their combined measures were able to account for 87 percent of the differences in brain size. Size did tend to increase as hominids migrated to higher latitudes. But temperature, seasonal changes or parasites weren’t very big factors.

What stood out significantly was population density. And here’s where Geary’s Survivor-style scenario comes in. As hominids evolved skills like tool-making that gave them control over their environments, their populations grew so large that they overwhelmed local supplies of game and fish and plants to forage. This unsustainable growth led to population crashes that were followed by resurgent growth and more crashes.

It was a cycle similar to what 19th-century British economist Thomas Malthus proposed during the upheaval of the Industrial Revolution. Population growth, Malthus argued, would always outpace agricultural production, leading to famines and death.

Geary, however, saw a positive side to such catastrophic cycles: Intellects could evolve to boost the survival odds.

Individual hominids with greater brain power would tend to have an advantage in achieving higher social status, Geary reasoned. “And when a population crashes, there seems to be an inverse relationship between social status and mortality,” he says. “People get hungry, tensions rise, they become less egalitarian.”

If a crash killed off the bottom half of the social status ladder, the average intellect of those who remained would be significantly higher. What was the 75th percentile, say, would become the 50th. With each population boom and bust, the average IQ would rise. These cycles also may explain why hominids journeyed out of central Africa in the first place, Geary says.

“The migration itself suggests increases in population. The reason to leave is that there aren’t enough resources, or you’ve been forced out.” Those population pressures occurred wherever hominids settled, which would explain why hominid brains grew larger in central Africa as well as on distant continents.

Not all evolutionary psychologists are persuaded. Gordon Gallup Jr. of the State University of New York at Albany did some of the primary research that found relationships between cooler temperatures and seasonal changes and the growth in hominid brain capacity. He suggests Geary may have gotten his conclusions about population density backwards.

“Increases in brain size and the effect this had on human intelligence is what may have led to the adaptations and technological developments that made higher population densities possible, not vice versa,” Gallup says.

But Geary holds that the kinds of intelligence that evolved from population upheavals provided hominids with better skills to deal with unpredictable situations, especially complex social situations. Tool making came early. Basic social skills such as recognizing facial expressions could have been “hard-wired” in the brain as well. “What’s more novel is the ability to think about relationships,” Geary says. “On Survivor, whatever they do, they have to think ahead. They have to think of the skills and interests of the other people on the island.” The situations, solutions and outcomes are always different, he says. “Otherwise, there would be just one season of Survivor.”

There are several components to this kind of survival intelligence: An individual will do better if he’s able to keep his reactions to events under control and coolly reason through the problems. Another advantage is the ability to perform mental “time travel.” This has nothing to do with science fiction; it’s simply the power to mentally recreate past experiences and to look forward in time to create scenarios of what might happen in the future.

Time travel may have given hominids the ability to strategize social maneuvers. The motivation to exert social control may have come from increasingly fertile imaginations. “Maybe what was going on is we developed a kind of imaginary self-centered perfect world,” Geary says. “Wouldn’t everything be better if they did things the way you want it? People tend to develop very rich fantasy worlds where they’re in control.”

Geary presents all these ideas in absorbing depth in his book The Origin of Mind: Evolution of Brain, Cognition, and General Intelligence. Published in 2005, the book got rave reviews in the academic press. “Make no mistake about it, The Origin of Mind is impressive,” wrote a reviewer in the Journal of Evolutionary Psychology. “It constitutes a huge interdisciplinary synthesis of research on the brain, cognition, and intelligence... We enthusiastically endorse this book.”

Geary wasn’t always confident he would get such a keen response to his ideas on evolution. In fact, he bided his time and waited until MU granted him tenure to start publishing on the subject. At a time when social explanations of behavior held sway, evolutionary psychology was controversial, politically incorrect.

Side profile of David Geary

David Geary: An evolutionary spin on psychological research.

“A lot of people don’t like this approach,” he says. “You could get a lot of flack, particularly in the ’90s, for looking at evolutionary explanations. So I put all that on hold. Once I got tenure, it didn’t matter.”

In the 1980s, as a graduate student at the University of California, Riverside, Geary studied neuropsychological development, math cognition and individual differences in learning. He also developed an interest in evolution. But that was something he had to cultivate on his own. At that time, “there was no evolutionary psychology,” he says. “Everybody in my generation is pretty much self-taught.”

Geary also pursued parallel intellectual pursuits. His first line of research was in cognitive psychology, first at the University of Texas, El Paso, then at the University of Missouri-Rolla (now the Missouri University of Science and Technology) before arriving at MU in 1989. He developed a national reputation for his work into how children learn mathematics. Geary’s first book, published in 1994, was Children’s Mathematical Development.

During President George W. Bush’s administration, Geary was appointed to the National Mathematics Advisory Panel, a group charged with studying how to get students through high school algebra successfully. Its thick final report came out in 2008. “We don’t compare well [to other countries] and we need to improve,” Geary says.

Geary is in the midst of the MU Math Study, a 10-year project that follows schoolchildren from kindergarten through ninth grade, comparing how students with learning disabilities and their peers develop math skills. He has also, over the years, kept thinking about evolution, reading and preparing.

In 1998, for example, he came out with the book Male, Female: The Evolution of Human Sex Differences, a discussion of human sex differences from the perspective of Darwin’s principles of sexual selection. In the simplest terms, men compete to become successful in their cultures and this, in turn, helps them to attract mates. Women, who pay a greater price in reproducing with pregnancy and breastfeeding, are more selective. They look for signs that a male is culturally successful, healthy, and thus more likely to produce healthy offspring.

But Geary’s book, recently reprinted in a revised and expanded second edition, covers a lot more ground than just mating strategies. There are evolutionary explanations for differences in physical attributes, how children play, and differences in academic skills and occupational choices. Male, Female also got stellar reviews from evolutionary psychologists and biologists. But it wasn’t well received by some feminists, Geary says.

Such theories simply justified prevailing stereotypes of nurturing women and philandering men, critics charged. “I got a lot of flack, but being socially insensitive helped,” he quipped. “Any speculation that the differences may be biological and not socially constructed was unwelcome.”

But since the book came out, Geary has become a go-to expert on gender differences.

When, for example, then-Harvard president Lawrence Summers drew criticism in 2005 for suggesting that differences in aptitude may account for the relatively small number of women holding high academic positions in math and engineering, pundits were quick to cite Geary’s work. “Some scholars, notably David Geary of the University of Missouri-Columbia, have argued persuasively that this premise is in fact required by the logic of Darwinian natural selection,” wrote a columnist for Forbes magazine.

When not pursuing research, Geary stays in touch with his primal male by practicing the Korean martial art, Taekwondo. He started doing it as a father-son activity 14 years ago. “My son doesn’t go much now, but I do,” Geary says. He’s competed in tournaments and now holds a second-degree black belt. “I like to hit and kick people,” he says wryly. “Good exercise.”

Geary’s son is 20 now and a student at MU. He has a daughter, 24, in law school. Next up for evolutionary psychology: A study on sex differences and vulnerabilities. Geary and Bailey will be combing through a National Institutes of Health database that contains a trove of physical, social and academic information on a large group of subjects from before they were born to beyond their high school careers.

Males, in general, show greater variations in intelligence and other traits, Geary says. But males also are more sensitive to environmental conditions. Geary’s prediction is the data will show that boys are more vulnerable to risk factors. They will be more likely to have poorer grades than girls if they come from an alcoholic household, for example. “Who’s the most sensitive sex in terms of growth and social functioning? It should be interesting,” he says.

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University of Missouri

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