Human: The Science Behind What Makes Us Unique - Michael S. Gazzaniga (2008)



It is good to rub and polish our brain against that of others.

Michel de Montaigne

IMAGINE: YOUR STOIC DAUGHTER COMPLAINS OF ACUTE ABDOMINAL pain while you are on vacation. You know that if she is complaining, then it is serious. You arrive at the ER with your wife and daughter, and the surgeon on duty, a total stranger, after a two-minute examination, says an emergency appendectomy is in order, now. You remember that a high-school buddy is a doctor in town, miraculously reach him on the phone, and get the reassurance that your daughter is in good hands. Everything is a go, and the surgeon is let into your new alliance. Old alliances are reestablished, new alliances are formed, and there is a successful surgery—followed by breaking of these fresh, fleeting alliances. The social mind is at work.

Imagine: You have signed on to take a guided trip to a rather adventurous locale, a place you would not attempt on your own. You are meeting with your group and guide the first morning. Glancing around at unfamiliar faces, you wonder, What was I thinking? However, two days later, you are clambering up a narrow winding path, trusting a person you have known for only forty-eight hours. Later you are having an interesting lunch conversation with a nearly complete stranger, and that evening you are asked to join a small group for dinner. By the end of the week, the tour group you are in has divided itself into subgroups, which in turn have subgroups. The coalitions shift by the minute. The social mind is abuzz with ties being made and broken and, among other things, the phenomenon of human politics is apparent.

Forming and reforming social groups and alliances are what we do all the time. This is the big picture. And yet many experimental scientists like me have focused on pieces of the big picture. We have been struggling to grasp what may well be inherent fundamental cognitive skills that enable us to form categories, deal with quantity, or assemble piecemeal sensory input into wholly perceived sensations. We have not focused on what the human brain does best, what it seems built to do: think socially.

It is all about social process. Although we are highly skilled at categorizing people, animals, and things, we don’t think about triangles and squares and red and blue. I don’t look at the person walking down the street with a dog and think, “Well the head is a circle, the torso a triangle, and whoa, lookee there, four rectangular extremities, well, I guess I should say cylindrical, and then, well, we’ve got those ten cylindrical fingers…now for the dog.” The fact is, we evolved with lots of other humans around, and developed brain capacity to monitor social behavior in large groups so that we may assess the value of cooperation, the risk of noncooperation, and so on. When one wakes up to this fact, that we are a bunch of party animals, not solitary hermits or mere perceptual data evaluators, suddenly a new question presents itself. If we are so social, how did that happen? Where did that come from? Were our ancestors social? How can natural selection result in group cooperation? Does natural selection work only to select for individual cognitive traits? Or does it work to select for group behavior as well?

This core issue grabbed the attention of Charles Darwin. While he pushed the view of the survival of the fittest, he was well aware of the seemingly paradoxical fact that many creatures make themselves less fit so the group may survive. In the worlds of bees and birds, this goes on all the time, and these phenomena have given rise to the view that natural selection must work on whole groups. Indeed, such mechanisms could well serve as the cornerstone for the emergence of human social and ethical behavior.

That was all fine until the great evolutionary biologist George Williams put the idea of group selection to rest (for a while). In an interview, he recounted his insight that “natural selection works most effectively at the individual level, and adaptations that are produced are adaptive for those individuals, in competition with other individuals of the same population, rather than for any collective well-being.”1 Natural selection is not the mechanism at work on social processes and norms, which come into and out of existence so quickly. Individual selection also means that living organisms are not adapted to prevent the extinction of their own species. Organisms would be wily at preventing only their own personal extinction. Williams’s “adaptationist” paradigm has dominated thinking in evolutionary biology for the past forty years.

Armed with Williams’s analysis, Richard Dawkins, the evolutionary biologist who holds the Charles Simonyi Chair for the Public Understanding of Science at Oxford University, took it further and became the vanguard for the idea of the selfish gene. On reading the idea that natural selection works only on genes, one might argue that altruism and all other ideas that favor groups were incidental. It is easy to imagine that this sort of thinking was loathed by many, including the well-known paleontologist and evolutionary biologist Stephen J. Gould, who referred to the core belief that natural selection works only on genes as “Darwinian fundamentalism.”

Dawkins had also built on the work done by William Hamilton in the early 1960s at the London School of Economics and the University College London, who had established a Darwinian view for altruism. Hamilton worked on kin selection, and was able to show by a simple mathematical formula (C < R × B, where C is the cost to the actor, R is the genetic relatedness between the actor and the recipient, and B is the benefit to the recipient) that our human preference for altruism has a rationale using models of shared genes.2 This implied a limited restraint on selfish competitive behavior and the possibility of limited self-sacrifices. If you were closely enough related, it would make genetic sense to help out a relative. He went on to suggest that such behavior supported general biological principles of social evolution. In short, Hamilton had given both Darwin and the selfish-gene thinkers a unified way of comprehending the problem of altruism. He had worked out how fitness worked on individuals other than the actor. This became known as Hamilton’s principle, and it is brilliant.

Still, not everyone is happy denying the role of group selection as a player in evolution. Although Dawkins, Williams, and other critics of group selection admit that natural selection can work on groups in principle, their stance is that selection pressures at the individual level are always stronger than those at the group level. Not all evolutionary biologists agree. David Sloan Wilson and Edward O. Wilson, in a review of the history of the rise and fall of group selection theory, conclude that the last forty years of research have provided new empirical evidence that supports the theory of group selection and its theoretical plausibility as an evolutionary force. “The problem is that for a social group to function as an adaptive unit, its members must do things for each other. Yet, these group-advantageous behaviors seldom maximize relative fitness within the social group. The solution according to Darwin is that natural selection takes place at more than one level of the biological hierarchy. Selfish individuals might out-compete altruists within groups, but internally altruistic groups out-compete selfish groups. This is the essential logic of what has become known as multilevel selection theory.”3 David Sloan Wilson suggests that group selection is not just a significant evolutionary force but can sometimes be the dominating evolutionary force. In a letter to eSkeptic, he writes: “It turns out that evolution takes place not only by small mutational change, but also by social groups and multi-species communities becoming so integrated that they become higher-level organisms in their own right.”*

Although this is a highly controversial question, we can let the evolutionary biologists duke it out. Let us merely come away with the fact that our social behavior has biological origins.

The deep biological forces at work in producing our social mind will become evident as we consider how we got to this place. Even more tantalizing is the possibility that all those social relationships we now worry about so intensely are merely by-products of behavior originally selected to avoid our being eaten by predators. Natural selection mandated us to be in groups in order to survive. Once there, we construct our “meaningful” as well as our “manipulative” social relationships, with our interpretive minds ever busy dealing with the stuff around us, most of which involves our fellow humans. While those human social relationships become central to our mental life, indeed become in many cases the raison d’être of our lives, it is all generated by a process secondary to the real reason we fall into social groups. We now think about others all the time because that is how we are built. Without all those others, without our alliances and coalitions, we die. It was true, as we shall see, for early humans. It is still true for us.

What would you think about if you were the only person on earth? Maybe your next meal? However, you wouldn’t be thinking about who might help you get that meal or with whom you might share that meal. You might think about how to avoid being a meal yourself, but there would be no one to help you watch for predators.

We are social to the core. There is no way around the fact. Our big brains are there primarily to deal with social matters, not to see, to feel, or to cogitate about the second law of thermodynamics. We all can do these personal and more psychological actions. We can develop rich theories about our personality, but we do so as a result of functioning in the social world. All of that comes along after the fact. And the fact is, in order to survive and prosper, we had to become social. So, understanding how we got here requires reviewing evolutionary biology, and to understand the biology of our current social abilities, which include phenomena such as altruism, we need to remind ourselves how evolution works.


Charles Darwin and Alfred Wallace* both observed that although species have a high potential for reproduction and populations should multiply exponentially, they don’t. Except for occasional fluctuations, populations remain stable. After all, natural resources are limited and remain constant in a stable environment.* Thus more individuals are born than the resources can support, and this results in competition for those resources. Darwin and Wallace also observed that within each species, the individuals in the population vary. No two are exactly alike, and many of the traits that are variable are inherited. They concluded that the chances for survival weren’t random, but varied with the heritable characteristics. According to the laws of natural selection, for any characteristic to be selected in a competitive environment, it has to provide a survival advantage to the individual. That advantage must manifest itself in a greater number of surviving offspring. The characteristic may allow the individual to be more successful at finding food (so he is stronger and healthier and hence can reproduce more and longer), at mating (so he will reproduce more), or at fighting off predators (so he will live longer and be able to reproduce more). These characteristics are coded for in the individual’s genes and are passed on to the next generation. Thus, genes that code for any behavior that increases reproductive success will become more prevalent in the population.

Competitive pressures are affected by climate, geography, and other individual animals, both within the species and from different species. Changes in climate and geography, such as a volcanic eruption that also affects the climate, can cause changes in food resources, making them either more or less plentiful. Social competition arises within a species, either for food resources or sexual partners. Different species have evolved to deal with food competition in different ways. Some share and some don’t.

One of the questions that puzzled Darwin about his theory was concerning altruistic behavior. It didn’t make sense that an individual would share—would ever provide anything to another individual that would decrease its own reproductive success to the benefit of another’s. Yet this happens frequently in species that live in groups. As I already mentioned, William Hamilton in 1964 came up with the theory of kin selection, which explains this behavior. Altruistic behavior could evolve if the benefiting individuals were genetically related to the provider. Parents will sacrifice for their children, who share 50 percent of their DNA; individuals also share 50 percent of their DNA with their siblings; their grandchildren and their nieces and nephews share 25 percent of their DNA. Helping your close relatives survive and reproduce also passes your genes on to the next generation. It doesn’t matter how the genes get passed, just so they do.

Kin selection does not explain all cases of altruism, however. Why would anyone do a favor for a friend? This question remained unanswered until Robert Trivers, professor of anthropology at Rutgers University, figured it out. If an individual does a favor for an unrelated individual and is sure it will be returned at a later date, then that could provide a survival advantage.4 This presupposes several things, of course. One is that an individual can specifically recognize another individual and has the ability to remember that a favor was done. Another is that the two live in close enough contact that predictable occasions will arise to get repaid. They also have to be able to evaluate the cost of the favor and make sure that the one they get in return is of equal value. This is called reciprocal altruism, and it is very rare in the animal world.*

The difficulty arises because there is a time lag between when one individual performs a favor and when the second reciprocates. The time lag could allow for cheating. If the second individual is not reliable, it is not in the interest of the first to cooperate with him, and the possibility of a cooperative system falters. Species that practice reciprocal altruism also have mechanisms to identify cheaters,5 otherwise the behavior would never have survived. As a consequence, strict Darwinian principles can help explain such phenomena as altruism. During the Enron fiasco, the cry was “Follow the money.” In biology, follow the genes.

This leaves one further problem: The old question, why leave a tip at a restaurant that you will never return to? We will get to this question later, and it may have to be explained by group selection!

Sexual Selection and Social Groups

Some adaptations enhance success in reproductive competition. The classic example is the peacock’s tail. Common sense would tell you that it could only be a hindrance towing a huge tail around. How could that possibly be adaptive? However, any bird that could survive with a big tail must surely be an attractive mate: strong and healthy and wily. That big tail is straight from Madison Avenue, a great advertisement campaign that pays off with more mates. The birds with the big tails have more offspring.

The peacock’s tail confers an advantage for sexual selection, the term for the social dynamics involved in mate selection and reproduction. That tail is known as a fitness indicator. The higher the cost of a fitness indicator to the individual, the more reliable it is. It costs the peacock a lot of energy to carry around and maintain the big tail. He cannot counterfeit it; it is a reliable fitness indicator. A guy with a new Chevy may well have counterfeited his fitness indicator; he could have bought it with 0 percent financing, no credit, and a low monthly payment. However, a guy with a Lamborghini has an expensive, high-maintenance car that cannot be purchased without good credit, and it reliably indicates his resources. A Lamborghini is a good fitness indicator, but a Chevy is not.

Trivers also helped us realize that the underlying behavior of sexual selection all revolves around parental investment. Parental investment is “any investment by the parent in an individual offspring that increases the offspring’s chance of surviving at the cost of the parent’s ability to invest in other offspring.”6 Hence, in any species, the sex with the higher potential rate of reproduction is more concerned about mating as often as possible (to get as many of their genes into the next generation as possible), and the sex with the lower reproductive potential is more concerned about parental care, to make sure that the few offspring they have will survive.7 In 95 percent of mammalian species, there is a large difference between males and females as to the efforts invested in mating and parenting.8 Females have limited reproductive time, due to pregnancy (internal gestation) and care of young offspring (lactating).9 And we all know about males. They are ready to reproduce at a moment’s notice.

The sex that has a higher parental investment and lower reproductive potential, usually the female, tends to be more fussy about mate selection.10 They have more to lose by making a bad decision (less fit offspring that might not be able to reproduce themselves). Female choice of mating partners has influenced physical (the peacock’s tail), behavioral, and social evolution in males. It intensifies both male-male competition for mating partners and female-female competition. Sexual selection can lead to “runaway sexual selection.” This means the genes that are being selected for are also doing the selecting, setting up a positive feedback loop. Let me give you a simplified example of how this works.

Say you have a population of rabbits with short ears. Along with other characteristics, the trait for ear length is variable and heritable. The male rabbits have little parental investment; they mate as often as they can with whomever they can. Now, although they all have short ears, Rex’s ears are a little longer than the others’. For some reason, a couple of the females have evolved a preference for longer ears, so they choose to mate with Rex. Their offspring are not only going to have longer ears but also will have the preference for longer ears. The traits have become genetically correlated when genes for different traits (long ears and the preference for long ears) end up in the same bodies. A positive feedback loop has been established. The more females who select for long ears, the more males and females there will be who have long ears as well as the preference for long ears. Runaway selection occurs.

Big Brains, Big Appetites, and the Hunt

The third factor in our drift toward being social seems to grow out of our need to nourish our ever-growing big brains. Hunting, herding, hiding, and hustling all lead to our social instincts and ultimately our domination. One way to compare brain sizes was used by David Geary, now professor of psychology at the University of Missouri, who has estimated what is called the encephalization quotient, or EQ,* of various hominid species as a percentage of the EQ of modern humans. He has shown that there is a relentless progression of increasing relative brain size during the evolution of hominids.11 What caused this progression?

Traditional theories propose that ecological problems and problem solving have driven changes in the brain. Harry Jerrison, paleoanthropologist and emeritus professor of psychiatry at the University of California at Los Angeles, noted the brain sizes of predators and prey have increased back and forth in tit-for-tat fashion over the last sixty-five million years.12 Because humans use tools for hunting (predation), it was assumed that production and use of tools were what was driving the increase in brain size. However, this theory didn’t fit the facts.

Thomas Wynn, an anthropologist at the University of Colorado, states, “Most of the evolution of the human brain, the presumed anatomy of intelligence, had occurred prior to any evidence for technological sophistication and, as a consequence, it appears unlikely that technology itself played a central role in the evolution of this impressive human ability.”13 That is not to say that the ecology was not the early driving force for increased brain size, just that tool use was not.

Big brains are expensive and require more energy (food) than small ones, and there is evidence that early hominids did become more efficient at hunting and foraging and were thus able to occupy a wider range of ecologies. Anthropologists John Tooby and Irven Devore argue that hunting was very important in human evolution. As Steven Pinker puts it, “The key is to ask not what the mind can do for hunting, but what hunting can do for the mind.”14 And what it can do is supply meat, a complete protein and a great source of energy for the greedy brain. Pinker points out that in the land of mammals, those that are carnivores have bigger relative brain sizes.

Richard Wrangham, our chimp man, thinks having meat was not enough; one had to be able to eat it efficiently. Although the diet of a chimpanzee contains about thirty percent monkey meat, it is very tough and it takes so long to chew that any advantage it might have in total calories is offset by the time it takes to eat. That is, an equivalent amount of time eating plants would have supplied the same number of calories. Wrangham not only spent many hours observing chimp behavior, he also sampled their cuisine, and he wasn’t impressed. It was tough, fibrous, and very difficult to chew. He could not understand how any ape, eating the diet of a chimp—raw fruits, leaves, tubers, and monkey meat—could amass enough calories to supply the metabolically expensive big brain. Chimps spend almost half their waking hours chewing, interspersed with short periods of rest, which allow their stomachs to empty, but not enough time to go on extended hunts. There just wasn’t enough time in the day to eat enough calories.

There also was another quandary. Chimps have big teeth and powerful jaws, as did the early Australopithecines and Homo habilis. Homo erectus was a different story. His jaws and teeth were smaller, while his brain was twice as large as his predecessor Homo habilis. What was he eating to get the calories to drive and maintain the brain expansion with those wimpy teeth and jaws? Not only that, Homo erectus had a smaller rib cage and abdomen, meaning that it could not hold as large of a digestive tract as Homo habilis. In fact modern man has a 60 percent shorter digestive tract than predicted for a great ape of our size.

Starting into the fire, Wrangham came up with a radical idea: those early humans were eating barbeque!15 Cooked food has several advantages over raw food.16 It actually has more calories, and is softer, so you don’t have to spend so much time and energy chewing: more calories, less time, less effort (not unlike the modern concept of fast food). In fact, the softer the food, the more calories there are available for growth, because it takes less energy to consume and digest it.17, 18 Some anthropologists have objected to this theory because the oldest evidence for fire that they have found is from 500,000 years ago, but there are some hints surfacing that fire was on the scene much earlier, maybe even 1.6 million years ago, just about the time that Homo erectus made his appearance. Wrangham suggests that Homo sapiens are biologically adapted to eat cooked food.15 He thinks that cooking food drove the expansion of the brain by increasing calories and decreasing the amount of time it takes to ingest them. This freed up more time for hunting and socializing.

There are those, however, who think the story hinges on the fatty acids in the brain. The long-chain polyunsaturated fatty acid docosahexaenoic acid (DHA) was required for the expansion of the hominid cerebral cortex during the last one to two million years. Michael Crawford and coworkers at the Institute of Brain Chemistry and Human Nutrition, University of North London, think that because biosynthesis of DHA from its dietary precursor (alpha-linolenic acid, or LNA) is relatively inefficient, expansion of the human brain required a plentiful source of preformed docosahexaenoic acid.19 The richest source of DHA is the marine food chain, while the savanna environment offers very little of it. Tropical freshwater fish and shellfish have long-chain polyunsaturated lipid ratios more similar to that of the human brain than any other food source known. Crawford concludes that Homo sapiens could not have evolved on the savannas but instead were holed up at the beach, gathering along the shoreline.20 Nutrients gained in this manner contributed to increasing brain size and intelligence, which allowed our ancestors to forage and fish more effectively.21

But anthropologists Bryce Carlson and John Kingston at Emory University are not convinced. They do not think the biochemistry implies any such thing. They point out that the key premise of this perspective—that biosynthesis of DHA from LNA is not only inefficient but also insufficient for the growth and maturation of an encephalized brain—is not well supported. To the contrary, evidence suggests that consumption of LNA available in a wider variety of sources within a number of terrestrial ecosystems is sufficient for normal brain development and maintenance in modern humans and presumably our ancestors.22

By moving out into the more open landscapes—open woodlands, savannas, and grasslands—the early hominids not only had more animals to hunt, they also became more of a target for predators themselves. There is a growing consensus that a major factor in developing larger brains was the banding together in social groups, which made hunting and gathering more efficient and also provided protection from other predators.23

There are two ways to outfox predators. One is to be bigger than they are, and the other is to be part of a larger group. (Gary Larsen, in a Far Side cartoon, presented a third method: All you need is a buddy who runs slower than you do.) The more individuals in the group, the more eyes are on the lookout. Predators have an attack range that depends on their speed and their style of killing. As long as you spot them and stay out of their range, you are fine. Also, if you have compatriots who will come to your aid when you are in trouble, a predator is less likely to attack. Herd animals are not known for the buddy system, but the social primates are. Individuals that banded together had a higher survival rate. And this brings us to social groups.

So three intertwined factors triggered the push toward our social mind: natural selection, sexual selection, and the consequences of needing more food to nourish our growing brains. Once social abilities became part of human brain architecture, other forces were unleashed, which in turn contributed to our growing brain size.


In 1966, Alison Jolly, a behavioral biologist trained in America and now at the University of Winchester in the United Kingdom, concluded a paper about lemur social behavior by stating, “Primate social life provided the evolutionary context of primate intelligence.”24 In 1976, Nicholas Humphrey, without knowledge of Jolly’s paper, also concluded, “I argue that the higher intellectual faculties of primates have evolved as an adaptation to the complexities of social living.”25 He was suggesting that the ability to predict and manipulate another’s behavior would give a survival advantage and would lead to increased mental complexity. Upon these and a few other papers, the theory of Machiavellian intelligence was hatched.

The hypothesis was first presented by Richard Byrne and Andrew Whiten at the University of Saint Andrews, Scotland, and they suggested that the difference between primates and nonprimates is the complexity of their social skills: Living in complexly bonded social groups is more challenging than dealing with the physical world, and the cognitive demands of this social life selected for increases in brain size and function.26 “Most monkeys and apes live in long-lasting groups, so that familiar conspecifics are major competitors for access to resources. This situation favours individuals that can offset the costs of competition by using manipulative tactics, and skillful manipulation depends on extensive social knowledge. Because competitive advantage operates relative to the ability of others in the population, an ‘arms race’ of increasing social skill results, which is eventually brought into equilibrium by the high metabolic cost of brain tissue.”23 Poor Machiavelli. Perhaps he was the ultimate sociologist, but his name has pejorative connotations, so the messenger was shot. The theory is now called the social brain hypothesis.

Another related hypothesis on increasing brain size was suggested by Richard Alexander, a professor of zoology at the University of Michigan. He focused on intergroup rather than intragroup competition and proposed that the main predator became other groups of hominids. This caused an arms race of strategizing and weapon invention: “Humans had in some unique fashion become so ecologically dominant that they in effect became their own principal hostile force of nature, explicitly in regard to evolutionary changes in the human psyche and social behavior.”27


Support for some type of social component for the big brain has come most notably from the very clever anthropologist Robin Dunbar at the University of Liverpool. Each type of primate tends to have a social group size consistent with other members of the same species. Dunbar has correlated brain size with social group size in primates and apes, and found there are two different but parallel scales, one for apes and one for the other primates. Both show that the bigger the neocortex, the larger the social group. However, the apes required a bigger neocortex per given group size than the other primates.28 They seem to have to work harder to maintain their social relationships.

But why is social group size limited? Does it have something to do with our cognitive abilities? Dunbar proposes five cognitive abilities that could be limiting social group size: the ability to interpret visual information to recognize others, the memory for faces, the ability to remember who has a relationship with whom, the capacity to process emotional information, and the ability to manipulate information about a set of relationships. He maintains that it is the last cognitive skill, the one that deals with social issues, that underlies the limitation on group size. He points out that vision doesn’t seem to be the problem, because the neocortex has continued to grow, whereas the visual cortex has not. Memory isn’t the problem; people can remember more faces than their predicted cognitive group size. Emotion doesn’t seem to be the problem; in fact there has been a reduction in the emotional centers of the brain. According to Dunbar, it is the ability to manipulate and coordinate information and social relationships that is limiting social group size. One can only handle a finite amount of manipulation and relationships!

Ways to measure social skill and social complexity have been hard to find. Currently five different aspects of social behavior have been correlated with neocortex size in primates. The first to be identified was social group size.29, 30 Others are:

Grooming clique size—the number of individuals with whom an animal can simultaneously maintain a cohesive intimate relationship that involves physical grooming.31

The degree of social skill required in male mating strategy. This indicates that the advantages of individual male rank and power appear to be offset by social skill: You don’t have to be the big cheese to get the girl; you can also get her by charm.32

The frequency of tactical deception—the ability to manipulate others in the social group without the use of force.23

The frequency of social play.33

Dunbar looked for ecological indices that might also correlate with brain size: the proportion of fruit in the diet, the home range size, day journey length, and foraging style. There was no correlation between these and neocortex size. He concluded that most likely the increasing size of social groups was driven by the ecological problem of predator risk, and the pressures and complexities of living in the increasingly large social groups drove brain size expansion.34 So we ended up with these big brains all because we didn’t want to be the plat du jour? Let’s look at these five social skills and see if any aspect of them is unique to humans.


While the observed social group size of chimpanzees is 55, the social group size that Dunbar calculated from the neocortex size of humans is 150. How can that be, when we now live in huge cities, often with millions of people? However, think about it. Most of those people you never even have cause to interact with. Remember: Our ancestors were hunter-gatherers, and people didn’t start to settle in one place until agriculture was developed about ten thousand years ago. Today the typical size of hunter-gatherer clans, related groups that gather together once a year for traditional ceremonies, is 150. This is also the size of traditional horticultural societies and modern-day Christmas card lists in personal address books.35

It turns out that 150 to 200 is the number of people who can be controlled without an organizational hierarchy. It is the basic number used in military units where personal loyalties and man-to-man contact keep order. Dunbar states that it is the upper limit of the size of modern business organizations that can be run informally.36 It is the maximum number of people an individual can keep track of, whom he can have a social relationship with and would be willing to help with a favor.


Gossiping has a bad reputation, but researchers who study gossip have not only found it to be universal,37 they have found that it is beneficial, that it is the way we learn to live in society. Dunbar thinks gossip is the human equivalent of social grooming in other primates (and remember, the size of the grooming group correlates with relative brain size). Physical grooming takes up much of a primate’s time. The primates that spend the most time grooming are chimps, who do it up to 20 percent of the time.38 At some point during the evolution of the hominids, as groups became larger, an individual would need to groom more and more other individuals in order to maintain relationships in the larger group. Grooming time would cut into the time that was needed to forage for food. This is when, Dunbar argues, language began to develop.39 If language began to substitute for grooming, one could “groom,” that is to say, gossip, while doing other things, such as foraging, traveling, and eating. This could be how talking with your mouth full began.

However, language can be a double-edged sword. The advantages of language are that you can groom several people at once (more efficient) and you can get and give information over a wider network. However, the disadvantage is that you are vulnerable to cheaters. With physical grooming, an individual invests high-quality personal time. That cannot be faked. With language, a new dimension has been added: liars. One can tell stories displaced in time, so their veracity is difficult to assess, and while grooming is done among a group, where it is visible and verifiable to all, gossiping can be done in private, and its veracity is not challenged. But language can also help you out with this problem. You may be warned by a friend about a previously bad experience with a certain individual. As a social group gets larger and more dispersed, cheaters or free riders become harder to keep track of. Gossip may have evolved partly as a way to control the slackers.40, 41

Various studies have found that, on the average, humans spend 80 percent of their waking time in the company of others. We average six to twelve hours per day in conversation, mostly one-on-one with known individuals.42 What has been found out shouldn’t come as any surprise to you. Nicholas Emler, a social psychologist at the London School of Economics, has studied the content of conversations and learned that 80 to 90 percent are about specific named and known individuals, which is to say, small talk. Impersonal topics, although they may involve personal opinions on art, literature, religion, politics, and so forth, form only a small part of the total. This is true not only about chance meetings in the grocery store but also at universities and corporate lunches. You might think that the world’s problems are being discussed and settled over power lunches, but it is really Bob’s tee time, Bill’s new Porsche, and the new secretary that are getting 90 percent of the air time. If you think this is an exaggerated statistic, then think about all those annoying cell phone conversations you have overheard. Have you ever heard anyone talking about Aristotle or quantum mechanics or Balzac at the table next to you or in the grocery line?

Other studies show that two-thirds of the content of conversations are self-disclosure. Of these, 11 percent are about states of mind (my mother-in-law is driving me nuts) or body (I really want that liposuction). The rest are about preferences (“I know it’s weird, but I really like LA”), plans (“I am going to start exercising on Friday”), and the most talked about, doings (“I fired him yesterday”). In fact doings is the biggest category of conversations about others.42 Gossip serves many purposes in society: It fosters relationships between gossip partners,43 satisfies the need to belong and be accepted by a unique group,37 elicits information,44 builds reputations (both good and bad),43 maintains and reinforces social norms,45 and allows individuals to evaluate themselves through comparison with others. It may enhance status in a group, or it may just entertain.46 Gossip allows people to express their opinions, ask advice, and express approval and disapproval.

Jonathan Haidt, a psychologist at the University of Virginia who studies happiness, writes that “Gossip is a policeman and a teacher. Without it, there would be chaos and ignorance.”47 It is not just women who gossip, although men like to call it “exchanging information” or “networking.” The only time when men spend less time gossiping than women do is when women are present. Then more lofty subjects are discussed for about 15 to 20 percent of the time. The only difference between male and female gossip is that men spend two-thirds of the time talking about themselves (“and when I reeled that sucker in, I swear it weighed twenty-five pounds!”), whereas women spend only one-third of the time talking about themselves, and are more interested in others (“and the last time I saw her, I swear she had gained twenty-five pounds!”).48

Beyond the content of conversations, Dunbar also discovered that conversation groups are not infinitely large but are usually self-limiting to about four individuals. Think about the last party you went to. People drift in and out of conversation groups, but once you go over four people, they do tend to break up into two conversations. He says it may be coincidence, but he suggests a correlation with chimp grooming. If you take a conversation group of four persons, only one is talking and the other three are listening, or in chimp lingo, are being groomed. Chimps have to groom one-on-one, and their maximum social group size is 55. If we can groom three at a time, as indicated by conversation group size, then if you multiply our three grooming partners by 55, you get 165—close to our social group size that Dunbar calculated from the neocortex size of humans.


In working the gossip mill, a person is involved not only in information exchange but perhaps in manipulation and deceit. He may be deceiving his gossip partners in essence because he isn’t really talking with them to find out how they are doing; he may be mining information for his own purposes. He might even make something up so as to have more gossip to barter. These are two different issues. Let’s start with exchange. I mentioned before, in order for reciprocal exchange to work, cheaters have to be identified. Otherwise, cheaters, who benefit without paying the cost, would eventually take over, and reciprocal exchange couldn’t sustain itself.

Although there are cultural differences among groups of people, there are many universal behaviors.49 As we have seen, we can trace some of these behaviors back to our common ancestor with the chimps and beyond, and some are qualitatively different. The field of evolutionary psychology attempts to explain mental traits, such as memory, perception, or language, as adaptations—products of natural or sexual selection. It looks at psychological mechanisms in the same way that biologists look at biological mechanisms.

Evolutionary psychology suggests that cognition has a functional structure that has a genetic basis, just like hearts, livers, and immune systems, and has evolved by natural or sexual selection. Like other organs and tissues, these psychological adaptations are universally shared within a species, and they enhance survival and reproduction. Some traits are not controversial, such as vision, fear, memory, and motor control. Others are controversial but are becoming less so, such as language acquisition, incest avoidance, cheater detection, and sex-specific mating strategies. Evolutionary psychologists explain that a brain, at least in part, is made up of modules, which have developed specific functional purposes that are innate and have been selected for. Leda Cosmides, one of the first in this field, describes the search for these functions:

When evolutionary psychologists refer to “the mind,” they mean the set of information-processing devices, embodied in the human brain, that are responsible for all conscious and nonconscious mental activity, and that generate all behavior. What allows evolutionary psychologists to go beyond traditional approaches in studying the mind is that they make active use in their research of an often overlooked fact: That the programs comprising the human mind were designed by natural selection to solve the adaptive problems faced by our hunter-gatherer ancestors. It leads one to look for programs that are well-engineered for solving problems such as hunting, foraging for plant foods, courting mates, cooperating with kin, forming coalitions for mutual defense, avoiding predators, and so on. Our minds should have programs that make us good at solving these problems, whether or not they are important in the modern world.50

There are very practical reasons for looking at our behavior and abilities from an evolutionary standpoint. Cosmides points out:

By understanding these programs, we can learn how to deal more effectively with evolutionarily novel circumstances. Consider, for example, that the only information available to hunter-gatherers about probability and risk was the frequency with which they encountered actual events. It looks like our “stone age mind” has programs designed to acquire and reason well about frequency data. Knowing this, evolutionary psychologists are developing better ways of communicating complex modern data about statistics.

Let’s say you have a positive mammogram. How likely is it that you actually have breast cancer? The typical way of presenting the relevant data—in percents—makes this difficult. If you said that 1% of women randomly screened have breast cancer, and all of these test positive, but there is a 3% false alarm rate, most people mistakenly think a positive mammogram means they have a 97% chance of having breast cancer. But let me give you the same information in absolute frequencies—an ecologically valid information format for a hunter-gatherer mind: Out of every 1000 women, 10 have breast cancer and test positive; 30 test positive but do not have breast cancer. So: out of every 1000 women, 40 will test positive, but only 10 of these will have breast cancer. This format makes it clear that, if you had a positive mammogram, your chance of having breast cancer is only 1 in 4…that is, 25%, not 97%.50

Detecting Cheaters

Cosmides also came up with an experiment that she thinks demonstrates that the human mind has a special module designed to detect individuals who cheat in social exchange situations. She uses the Wason Test,* which asks you to look for potential violations of a conditional rule: if P, then Q. Many forms of this test have been devised to ascertain whether or not humans have specialized cognitive machinery for social exchange. Let’s see how you do with it:

There are four cards on a table. Each card has a letter on one side and a number on the other. Currently you can see R, Q, 4, and 9. Turn over only those cards that you need to in order to prove whether the following rule is true or false: If a card has an R on one side, then it has a 4 on the other. Got it? What’s your answer?

The answer is R and 4. OK, now try this one:

There are four people sitting at a table. One is sixteen, the second is twenty-one, the third is drinking Coke, and the fourth is drinking beer. Only those over twenty-one can drink beer legally. Who should the bouncer check to make sure the law isn’t being broken? That one is easier isn’t it? The answer is the sixteen-year-old and the beer drinker.

Cosmides has found that people have a hard time with the first type of question; only 5 to 30 percent of people get this one right, whereas with the second one, 65 to 80 percent of people get it right—not just at Stanford where she first tried it, but all over the world, from the French to the Shiwiar of the Ecuadorian Amazon, and not just adults, but three-year-olds as well. Whenever the content of a problem asks you to look for cheaters in a social exchange situation, people find it simple to solve, whereas if it is posed as a logic problem, it is more difficult to solve.51

After many more experiments across cultures and age groups, Cosmides has found in addition that cheater detection develops at an early age, operates regardless of experience and familiarity, and detects cheating but not unintentional violations. She thinks that this cheater detection ability is a component of a universal human nature, designed by natural selection to produce an evolutionally stable strategy for conditional helping.

There is even neuroanatomical evidence. This comes from a patient, R.M., who has focal brain damage that has caused impairment in his cheater detection, but who has entirely normal reasoning on similar tasks that do not involve social exchange.52 Cosmides says, “As humans, we take for granted the fact that we can help each other by trading goods and services. But most animals cannot engage in this kind of behavior—they lack the programs that make it possible. It seems to me that this human cognitive ability is one of the greatest engines of cooperation in the animal kingdom.”50

We are not the only ones who can detect cheaters in social exchanges. It has been shown to exist to a limited degree in brown capuchin monkeys, in experiments done by Sarah Brosnan and Frans de Waal.53 However, animals involved in reciprocal exchange make approximations. Humans want to be sure they are giving and getting the equivalent amount; approximations won’t suffice. Indeed, Marc Hauser at Harvard University thinks that our mathematical abilities evolved with the emergence of social exchange systems.54

Cheating the Cheaters

Can you cheat the cheater detection system? Probably not, as Dan Chiappe, a psychologist at the University of Toronto, has found. He showed that in social contract situations, people rated cheaters more important to remember than cooperators, looked at cheaters longer, remembered their faces better, and were more likely to remember social contract information about them.55

When cheaters have been detected, there are two things that can be done with them: Either you avoid them, or you punish them. Isn’t it easier just to avoid them? To punish a cheater costs the punisher time and effort. What’s to be gained? Recently Pat Barclay, from Cornell University, has done a laboratory study showing that in games with repeated encounters, players who punish cheaters gain trust and respect and are thought of as being group focused. The benefits of this increase in good reputation (which, you remember, is a fitness indicator for sexual selection) can offset the costs of being a punisher, and could be a possible explanation for how the psychological mechanisms of altruistic behavior evolved.56 Better not do anything that might lead to one of your competitors’ getting a better rep. What a stroke of luck that you saw Don with that sophisticated-looking blonde at the racetrack. Everyone wonders what he does on his days off. That tidbit ought to be a hot commodity in the world of gossip exchange back at the office, but how will you know if what you get back is true? If you can detect cheaters, does that mean you’ll know if someone is lying? Not really. That comes with reading facial expressions and body language. But I’m glad you brought that up because…

Intentional Deception

Although deception is known throughout the animal world, such as the piping plover that feigns injury to lead predators away from its nests,57 intentional deception may be limited to the great apes.58 And humans are the masters of deception. It is ubiquitous and begins in the morning when women put on makeup (to make themselves more beautiful or appear younger ) and perfume (to mask their own odor). Women have been using jewelry, hair color, and makeup for eons. One has only to cruise through the Egyptian section of the Louvre. Men are no strangers to deception either. They put on deodorant and brush their thin hair across their bald spots (as if that deceives anyone) or plop on their toupees and head out to their cars that they had to buy on credit.

Can you imagine a world where no one lied? It would be awful. Do you really want to know the answer to “Hi, how are you doing today?” Or hear “I’ve noticed that those five pounds that you’ve put on are all on your chin”? Lies are used for self-promotion in job interviews (“Sure, I know how to do that”), and when meeting new people (“This is your daughter? Isn’t she the sweetest thing!” rather than Rodney Dangerfield’s comment, “Now I know why tigers eat their young”).59 They’re used when meeting potential mates (“Of course I’m a natural blonde”).60

We not only lie to each other, we lie to ourselves. From 100 percent of high school students who rank themselves as having a higher-than-average ability to get along with others (a mathematical impossibility) to 93 percent of college professors who rank themselves above average at their work, self-deception is in play.61 Or how about “I get plenty of exercise” and “My kid would never do that.” To be a good liar, it helps not to know that you are lying or, in the case of psychopaths, not to care. In fact children are taught to lie by their parents (“Tell Grandma how much you love the lederhosen” and “Don’t tell Sammy he is fat”) and by teachers (“I don’t care if you think Joe is dumb, it is not nice to say so”).

How do we tell if someone is lying? Do we really want to know? And why do we lie to ourselves?

How Do We Tell If Someone Is Lying?

While gossiping and determining if we think the information we are getting is true, we also read facial expressions. Face perception is probably the most developed visual skill in humans and obviously plays a major role in social interactions. It has long been thought that face perception is mediated by a specialized system in the human brain, and we now know that different parts of the brain mediate different types of face perception. The pathways that perceive identity are different from those that perceive movement and expressions.

Beginning soon after birth, babies prefer to look at faces rather than other objects.62 After the age of seven months, we begin to respond appropriately to specific expressions.63 Thereafter, face perception provides tons of information that greases social interaction. From the visual appearance of faces, one can access information about another person’s identity, background, age, gender, mood, interest level, and intentions. We can notice what they are looking at and check it out too, and also understand their speech better by lip-reading.64

We are not alone in the ability to recognize individual faces. Chimpanzees and rhesus monkeys are also able to do so.64 Contrary to what has previously been observed, recent dissection has shown that chimpanzees and humans have a nearly identical facial anatomy65 and a full range of facial expressions. Lisa Parr at Emory University has done some studies that demonstrate the ability of chimps to match photographic facial expressions with emotional scenes in videos.66 So we share with the chimps two components of gossiping and social exchange—recognizing with whom we are dealing and being able to read emotions from facial expressions—but will that help us in recognizing liars? Well, there is a whole range of facial and body movements that are associated with deception, which brings us back to our man Machiavelli.

Paul Ekman, at the University of California, San Francisco, has done more for the study of facial expression than anyone else. It was a lonely business when he started his studies, because everyone else—except Darwin, of course, and an eighteenth-century French neurologist named Duchenne de Boulogne—had avoided the topic. Ekman, through years of research, has established that facial expressions are universal67 and that there are specific expressions for specific emotions. When an individual is lying, the higher the stakes are, the more emotions (such as anxiety or fear) he is feeling.68 These emotions are leaked to the face69 and voice tone.70 And here is one of the benefits of true self-deception: If you don’t know you are lying, your facial expressions won’t give you away.

Ekman has studied people’s ability to detect liars, and it is pretty pathetic. Most people aren’t very good at it, even though they may think they are (once again deceiving themselves). They perform at the same rate as chance guessing. However, he has found some professionals to be good at it: Secret Service agents are the best, and next best are some psychotherapists. Out of twelve thousand people whom he has tested, he found only twenty who were naturally excellent lie detectors!71 One problem inherent in reading facial expressions is that one reads the emotion but does not necessarily understand the reason for the emotion and so misinterprets it. We will learn more about this in later chapters. You may realize that a person is scared and think it is because he is lying to you and is frightened that you will figure that out, but it could be that he is scared because he didn’t lie and is being falsely accused and he thinks that you won’t believe him.

Of course not all deception is nefarious. Out of politeness, people will often act as if they are enjoying themselves when they are not, such as complimenting you on the fish dish when in reality fish makes them gag. Or they are laughing at that really bad joke that you have already told too many times before. These are small-stakes lies without major repercussions.

People learn to manage their expressions, but Ekman has found microexpressions that result from trying to conceal emotions. Most people don’t see them, but you can learn to spot them. Fabricated expressions can also be hard to spot. For instance, the false smile: There are two muscles principally involved in real smiling, the zygomaticus major, which pulls the corners of the mouth up, and the orbicularis oculi pars lateralis, which, along with pulling up the cheeks and causing crow’s-feet, also pulls down the lateral border of the eyebrow. The orbicularis oculi muscle is not under voluntary control, so that in a fake smile the lateral border of the eyebrow does not depress, although a fully contracted zygomaticus can push the cheeks up to form crow’s-feet.

If we are good at spotting cheaters in social exchange, why do we find it hard to spot liars? Lying has become prevalent in the population, so wouldn’t mechanisms of detection have evolved? Ekman offers several explanations. First, he suggests that in the environment in which we evolved, lying wasn’t as prevalent because there were fewer opportunities. People lived openly in groups. The lack of privacy would have made the chances of detection high, and discovery would have been made by direct observation of behavior rather than having to rely on judgments of demeanor. Second, uncovered lies would have resulted in a bad reputation. Today, our environment is very different. Opportunities to lie abound, and we live behind closed doors. You can escape from a bad reputation, although it may be costly, by changing jobs, towns, countries, or spouses, and we haven’t been prepared by evolution to detect lies from demeanor. So why haven’t we learned how to detect them if we don’t have the power innately? Perhaps because our parents teach us not to identify their lies, such as stories to cover up sexual activity and who knows what all. It may be that we also prefer not to catch liars, because being suspicious rather than trusting makes relationships difficult to establish and keep. Or we may want to be misled because we have a stake in not knowing the truth. The truth may set you free, but it may also set you free with four kids and no income. Often the reason is politeness: What we are told is all that the teller wants us to know, and we don’t steal information that is not given to us.

But perhaps it is language, as it has evolved recently in humans, that is the problem. Understanding and interpreting language is a conscious process that involves much cognitive energy. If we are concentrating on what is being said, rather than letting visual perceptions and vocal clues register in our conscious brain, we may be lessening our detective powers. Gavin de Becker, in his book The Gift of Fear,72 advises people to trust the phenomenon that he defines as “knowing without knowing why.” He is an expert in predicting violent behavior, and he has found that most victims of violence have received warning signs without realizing it. Has our social training taught us not to detect deception? Do we reinterpret what we actually see? There is more work to be done.

Lying to Ourselves

Isn’t lying to ourselves counterproductive? As the saying goes, if you can’t trust yourself, then whom can you trust? Remember our cheater detector in social exchange? It pays to be cooperative, while being vigilant for cheaters. But you really don’t have to be cooperative. You just have to appear cooperative. All you need is a good rep. You don’t actually have to deserve it.

You mean being a hypocrite, right? Hypocrites make my blood boil.

Not so fast. Everyone (except for me, of course) is a hypocrite. It apparently is just easier to see from the outside than the inside. As we just learned, to pull this off, it helps not to consciously know that you are pulling a fast one, because then you will have less anxiety and thus less chance of getting busted.

Dan Batson at the University of Kansas has done a series of experiments73, 74 with rather shocking results. Students were given the opportunity to assign themselves and another student (actually fictitious) to different tasks. One task was more desirable (the chance to earn raffle tickets). The other task had no chance to earn raffle tickets and was described as boring. The students were told that the other participant would think the assignment was made by chance. They were also told that most participants thought that flipping a coin was the fairest way to assign the tasks, and a coin was provided for participants to flip if they wished. After the experiment, virtually all participants said that either assigning the other participant the better task or using the coin flip was more moral. Yet only about half flipped the coin. Of the nonflippers, 80 to 90 percent assigned themselves the better task and, contrary to the laws of probability, the same was true among those who flipped the coin. The students who flipped the coin all rated themselves as being more moral than the nonflippers, even when they fiddled with the results.

This outcome was replicated in numerous studies, even when the coin was labeled to avoid ambiguities in the coin toss. Some participants flipped the coin to appear fair, yet still served self-interest by ignoring the results and giving the better task to themselves—and still rated themselves as being more moral for simply having tossed the coin! That is called moral hypocrisy. The results were duplicated even when the students were told that after their decision they would have to tell the other participant how they arrived at it. With one discrepancy, more flipped the coin (75 percent) and reported this was how they had made the decision; however, the percent of flippers who gave themselves the better task remained the same. Batson states, “The benefits to oneself of moral hypocrisy are obvious: One can reap the material rewards of acting selfishly and also garner the social and self-rewards of being seen and seeing oneself as upstanding and moral.”

Participants who had scored highly on various moral responsibility tests were more likely to flip the coin, yet among coin flippers, the high moral scorers were no less likely to assign themselves the better task than were those who scored low. Thus, those with a greater sense of moral responsibility did not show signs of greater moral integrity; they actually showed signs of greater hypocrisy! They were more likely to appear moral (flip the coin) but no more likely to actually be moral (allow the coin flip to determine the task assignment).

The only time participants stopped cheating with the coin flip (and they all did) was when they made their decision while sitting in front of a mirror. Apparently, having to face the discrepancy between one’s stated moral standard to be fair versus unfairly ignoring the result of the coin flip was too much. Those who wished to appear moral had to actually be moral. Maybe we need more mirrors. That might help with the increasing obesity problem, too.

OK, so we lie to ourselves and have a difficult time spotting other liars. This isn’t good news for your gossip exchange quest. You may need to take one of Paul Ekman’s classes* on how to spot liars, but in the meantime, at least you can watch eyebrows and know that your coworkers aren’t going to be good at spotting your lies, unless the high stakes at the office make you a little more anxious.


Geoffrey Miller, an evolutionary psychologist at the University of New Mexico, has a problem with language. No, he can talk just fine. He is concerned about why it evolved. Most speech appears to transfer useful information from the speaker to the listener, and it costs time and energy. It seems to be altruistic. What fitness benefit can be attained by giving another individual good information? Reviewing the original argument of Richard Dawkins and John Krebs, Miller states, “Evolution cannot favor altruistic information-sharing any more than it can favor altruistic food-sharing. Therefore, most animals’ signals must have evolved to manipulate the behavior of another animal for the signaler’s own benefit.”75 And other animals have evolved to ignore them, because it didn’t pay to listen to manipulators. Those who did are not ancestors.

There are a few signals that are given credence: those that are reliable. These are the ones that say, “I’m poisonous,” “I’m faster than you,” or “Don’t even think about it, I’m stronger than you.” Then there are the warnings from relatives, like “There’s a leopard!” and the fitness indicators, like “Babe, have you seen my tail?” Miller concludes there are no credible models that can show evolution favors signals that carry any other kind of information, as long as there are incentives for deception. And when there is competition, there are always incentives for deception. Human language is a hotbed of deception because it can talk about other times and places when the listener was not present, such as: “The trout I caught yesterday was twenty-six inches.” Or “I left you a gazelle leg in that tree over the hill. Oh, gee, it’s gone? Musta been that lion.” “It has only been driven by my grandmother to the store and back.” And the infamous “I was working late at the office last night.”

How could reliable information-sharing have evolved? By sharing information, the teller does not necessarily lose his benefits. In fact, information-sharing could have benefits through kin selection and reciprocal altruism. Although Miller admits that this is mostly right, and probably how language initially emerged, when he looks at the real behavior of people, it doesn’t quite fit the predictions of kinship and reciprocity models. If you look at language as information, it brings more benefit to the listener than to the talker, so we should have evolved into great listeners and reluctant talkers. Instead of resenting the motormouth, or the self-absorbed talker, or the speaker who drones on for an extra fifteen minutes, we should be irritated with people who sit enthralled with what we say and make no effort to tell about themselves. Everyone has something to say, and in conversations people are oftentimes thinking about what they are going to say next rather than listening to the other person. Books on procedure have been written to make rules about who may talk when. We should have evolved huge ears and only a rudimentary speaking apparatus to gather what we could, rather than the elaborate ability to speak language and the more rudimentary hearing that we have.

Considering this conundrum, Miller proposes that language’s complexities evolved for verbal courtship. This solves the altruism problem by providing a sexual payoff for eloquent speaking by the male and the female. “Language complexity could have evolved through a combination of runaway sexual selection, mental biases in favor of well articulated thoughts, and fitness indicator effects.”75 Miller does not suggest that sexual selection accounts for the big brain in its entirety, just perhaps 10 percent.

A related theory has been presented by anthropologist Robbins Burling, who wondered why, when a rudimentary form of language was all that was needed for hunting, trade, and tool making, a more complex form emerged. He suggests that after language’s initial emergence, its increasing complexity was the result of male orators competing for social status, the most eloquent gaining reproductive advantages. He lists evidence of this reproductive advantage from various societies, ranging from the Yanomami to India and ancient Greece. Although his theory largely addresses the question of leadership, he concludes, “We need our very best language for winning a lover.”76

Hold on a minute. Are you saying that the big brain is for flirting? Does that mean that Frenchmen have the biggest brains?

It might. Get out the saws, we’ll have to do a study.

Consider what is involved in human courtship. If you are having a random conversation with someone, that person may be mildly skeptical. However, with courtship the stakes are high. If you are successful, it may pay off with offspring. You have to bring out the big guns because your listener is going to be highly critical on all fronts. She will automatically evaluate whether it makes sense, conforms to what she knows and believes, is at all interesting or novel, and whether she can begin to infer intelligence, education, social savvy, status, knowledge, creativity, a sense of humor, personality, and character. “How about those Sox?” is not going to do it for her. Remember how long it took Bill Murray to get the courtship right in Groundhog Day?

Verbal courtship is not limited to the one-on-one encounter. Public speaking also advertises your charms and status, as does anything that improves your intellectual cachet. As Miller states, “Language puts minds on public display, where sexual choice could see them clearly for the first time in evolutionary history.”75

This is a little confusing. If guys are so good at talking, how come they have the reputation of not communicating? And if males are selected for their verbal courtship abilities, how come it is women who have the reputation for being big talkers? Well, remember that verbal courtship is a two-way street and is considered a fitness indicator. That means it is difficult and costly in terms of time and energy that could be spent in competition for survival resources. Once he has his mate, it doesn’t pay the male to continue with the high-cost performance. Instead of talking his head off, he may get by with just a couple of sentences, unless sex is withheld, and then there may be a return of flowery speech. Women, however, have an incentive to continue their verbal courtship, because they want to keep the male around to help provide for their offspring.


This is a hard one to figure out. What is the point of social play? It uses a lot of energy and time, to accomplish what? No one really knows the answer to this question, but there are many ideas being batted around. It is generally thought that most youthful animal play is practice. Practice in stalking, chasing, and fleeing, a way to buff up physically,77, 78 develop motor and cognitive skills,79 hone fighting skills,80, 81 and become more physically adept at recovering from sudden shocks, such as loss of balance and falling over, and more emotionally adept at handling stressful situations.82 Think about a pile of kittens. However, Elisabetta Palagi, from the University of Pisa, who has studied play behavior in bonobos and chimps, thinks the theories about play have focused too much on long-term rather than immediate benefits, and this focus may have limited the understanding of some of the adaptive significance of play. This could be especially true about play behavior in adults. Although play behavior is most common in young animals, in many species, like chimpanzees, bonobos, and humans, adults also play.

But why do adults do it? Why do they play when they no longer need to practice? In a study of the chimpanzee colony housed in the ZooParc de Beauval in Saint-Aignan-sur-Cher, France—ten adults and nine immature chimps—she found that not only did the chimps groom each other the most just before chow time, but the adults and juveniles also played together the most just before chow time.83 Chimps are competitive, and feeding time is stressful for them. Grooming stimulates the release of beta-endorphins.84, 85 Palagi thinks grooming and play may limit aggression and increase tolerance, a contribution toward conflict management during periods of high stress. This would be an immediate benefit rather than a long-term one, and would be beneficial to both youngsters and adults.

Humans take social play to greater heights than the chimps and bonobos. One more theory for adult play comes from Geoffrey Miller, our sexual selection expert. He suggests that the increased cost of play with age makes it a reliable indicator of youthfulness, energy, fertility, and fitness. “Well, he had his eye on that young filly, and all of sudden he is out windsurfing and playing tennis again. He is acting like a teenager.” In fact, Miller says that the ability to invent and appreciate new ways of displaying physical fitness is a uniquely human ability, aka sports—the intersection of mind and physical strength.75 Another universal: All cultures have them. As with other animals, human males play in competitive sports more than females. In order to prevent competitors from killing each other, and to determine who wins, sports have come up with rules, although you might not realize it when watching soccer matches. Monetary rewards are a recent invention. In the past, the only reward was status, but that was good enough. Winning at sports is a reliable fitness indicator, and the reward is attracting high-quality sexual partners.


The shift to becoming highly social is what the human is all about. Lots of animals have some degree of social organization but none revel in it the way we do. As our brain became larger so too did our social group size. Something triggered our interest in the other guy, in living and cooperating in groups. Richard Wrangham has a captivating theory about the role of cooking as being the facilitator of such a huge shift in primate life. Other ideas include the need to fight off predators and to find food. Whatever the reason, others now argue that our higher intellectual skills arose as an adaptation to our newly evolved social needs. Understanding being social is fundamental to understanding the human condition.

With the importance of social groups now well understood, it is easy to see discussions emerge about whether or not natural selection might also work on groups versus individuals. It is a complex argument with much to say not only on both sides of the issue but also in the attempts to reconcile the question into theories that cover both sides. However these matters are finally settled and agreed to by all, here we are with big brains, living in social groups and better for it. As we move on, realizing our social nature is deeply rooted in our biology not simply in our cognitive theories about ourselves, we begin to see how the rest of our human equipment helps to guide us through the social maze.