Wired for Culture: Origins of the Human Social Mind

by Mark Pagel

  The wider picture of this public-spirited behavior is that our psychology has been shaped by the fact that our cultures have acted as units for our survival in a way that strongly linked our fates, and these are the conditions that favor public-spirited dispositions. In our natural state of living in hunter-gatherer cultural survival vehicles, everybody would have realized that everyone’s success at nearly everything they did would in some way depend upon the group pulling together. Sure, the hunter goes out and kills the meat himself (nearly all hunting of large prey is done by men), but think of the larger sphere of cooperative activity that makes his actions possible. Someone else is foraging while he is out hunting. Someone is guarding the village from raids, someone is looking after the children, and there will be other men with him assisting him on the hunt. Finally, someone had to make the various spears and nets and snares that are used in the hunt, not to mention all the other paraphernalia that make daily life possible: huts, vessels for carrying water, cured skins for clothing, baskets, and tools.

  Crucially this is not to say that we behave in a “group-selected” way or that we behave “for the good of our groups.” Rather, the nature of the food-sharing problem shows us how the conflict between what is best for you and what is best for your group can be resolved. I like to think of this as enhancement selection. You can actually do things that provide direct benefits to the group and at a cost to you, because those costs are more than erased by the enhancement of your reputation. As soon as this becomes possible, you might be encouraged to become public-minded about just about anything you were particularly good at because you can sell it for reputation points in your community. Maybe it is making good arrows or better hand axes, being good at fishing or knowing where to find the best berries. What looks like altruism on your part is actually just another stall in the reputation marketplace.

  PAROCHIALISM, XENOPHOBIA, AND

  THE PRINCIPLE OF INFORMATION

  SADLY, GIVEN our demographic success as a species, conflict has been inevitable throughout our history. We have seen the terrible violence that human groups are capable of directing at one another, and speculated that parochialism might be an emotion that arises to make it more likely you will vanquish a competing group in battle. And we have seen how false beliefs about another group can indeed make it easier to conduct violence against them.

  We can also see parochial views toward other societies arising from the way we have envisioned that cooperation works within human societies. Our cooperation depends upon acquiring high-quality and up-to-date information about others’ reputations. Lacking that information, as we saw from the principle of information, it has paid us throughout our evolutionary history to withhold cooperation simply as a way of avoiding providing help to people who might not share our dispositions. We acquire information about others’ reputations from observation, gossip, and word of mouth, and so the information we have on people from other groups will normally be well below that required to know whether we should cooperate. But it gets even worse than this. You and the members of your cooperative group know that the people in another group have formed their own allegiances: these people by being committed to their group have positively demonstrated their lack of commitment to yours.

  Our success as a species has lain in using our cooperative group to generate shared knowledge and technology. This shared resource clothes and feeds us, it protects us, it puts a roof over our heads, and it allows us to project ourselves into new territories. Would you give away things of such value without a fight or even just inadvertently to the wrong people? The costs are potentially so great that we might expect that natural selection has acted to make us wary of cooperating with strangers, and especially ones from other groups. Self-interested discrimination toward others based on group membership is not something we should condone, but it may have been a tactic that served us throughout our evolution.

  We don’t know if these scenarios are true, but there is little doubt that our all too common feelings of parochialism or xenophobia are directed at others because they are members of a particular group, not at them per se. Indeed, we could not direct our xenophobia at someone we don’t even know. Violence or aggression against members of our own group normally violates the trust that is the foundation of our social nature. But this same aggression, violence, and even killing members of other groups can both demonstrate a commitment to one’s own group and deliver valuable resources. In any other animal species we would not be surprised that these factors positively favor some forms of violence and murder. It bothers us because as human beings it conflicts so directly with our self-image as good and cooperative people.

  CHAPTER 7

  Hostile Forces

  That we owe our big brains less to inventiveness than to

  conflicts of interest among social minds engaged in an arms race

  to be the best at manipulating others

  IF OUR BRAINS were our necks, we would resemble a giraffe. In fact, so out of proportion are our brains to the size of our bodies, we would resemble a giraffe with an elongated neck. This is a book about how culture has sculpted our minds and behavior, not about our appearance and other physical traits. But it might just be true that it is in the nature of our brains that culture has had its most significant effects. We can say this because in many respects human beings are rather ordinary animals. We are not particularly fast runners, not particularly good at climbing trees, not all that strong, and not very tough—our odds would be poor in a fight against an angry baboon, which is just a fraction of our size. But we are intelligent. In fact, it could be said we are infinitely more intelligent than any other animal we know of, at least in this narrow sense. We are the only animal that continually constructs new lifestyles and ways of life on a scaffolding of progressive cultural evolution. Based on what we know about the other animals, we could wait forever and not only would they fail to make the progress we have made in the past 80,000 or so years, they would not even have changed their behavior substantially from what they do now. Were we to go away, returning in a million years, the chimpanzees would still be behaving as they almost certainly have for the previous millions of years, fishing for termites from the ground with the same kinds of twigs, blades of grass, or pieces of bark. The same is true of other animals. But not of us, and it is all down to our brains.

  Among all the millions of different species of animal, the mammals have unusually large brains for the size of their bodies, bigger than, say, those of comparably sized fish, or reptiles, or birds. Among the mammals, the primates—monkeys and apes—have larger brains for their size than other mammals. Among the primates, the Great Apes—orang-utans, gorillas, chimpanzees, and humans—have the largest brains, but even among the Great Apes, humans are exceptional. Our brains, at around 3.25 pounds (1,400–1,500 grams), are three to four times the size of a chimpanzee’s or a gorilla’s brain. They are the largest brain for a given body size of any animal known, roughly seven to eight times larger than expected of a typical 130–180-pound mammal. A giraffe’s neck, long as it is, is not seven or eight times longer than that of a comparably sized grazing animal such as an eland.

  Our species last shared a common ancestor with chimpanzees around 6 to 7 million years ago. That common ancestor probably had a brain that weighed around 300 to 400 grams, or less than 1 pound. The evolutionary route our lineage took for the first 3 million years after separating from this common ancestor is not well known. But already by around 2.5 million years ago, brains had enlarged to about 600 grams in the species called Homo habilis or handy man. The species we call Homo erectus, the first truly upright ape, arose around 1.8 to 2 million years ago in Africa, and had a brain size of around 800–1,000 grams, or about two thirds the size of our own, and already roughly twice the size of a chimpanzee’s brain.

  Homo erectus’ brains only slowly enlarged over the next million years, reaching around 1,200 grams by around 500,000–700,000 years ago in the species called Homo heidelbergens
is. Not long after, two lineages split off from this species, one leading eventually to modern humans, the other to the Neanderthals and their sister species the Denisovans. By 200,000 years ago, human brains weighed around 1,250 grams, and they reached their modern size of 1,400–1,500 grams by around 150,000 to 100,000 years ago. This means that in just the last 1 million years or so, the human lineage enlarged its brain by an amount equivalent to the entire volume of a chimpanzee’s brain.

  Brains are costly organs to own and maintain. They account for only about 2 percent of our weight, but they require perhaps 20 percent of our need for energy when we are at rest. When you come home from the office having used your brain all day, you can blame your tiredness on having to feed this hungry gas-guzzler. This means that the increasingly brainy ape we were becoming must have been paying for its intellectual profligacy by improved survival and success at reproduction. We might have received some help in supporting our large brains from an unlikely source, starting perhaps 250,000 to 300,000 years ago. Around that time, premodern humans stumbled upon the idea of using fire to cook. As Richard Wrangham describes in his book Catching Fire, cooking food enhanced the amount of energy our ancestors could extract from it. Even if fire alone does not tell us why we were on a trajectory toward having large brains, the ability to cook might have made them easier to feed and maintain.

  Some anthropologists suggest that inventiveness is the hallmark of modern humans and the obvious force that would have paid for our large and hungry brains. Neanderthals had brains nearly the same size as ours, but their brains were different, and one of the chief differences is given away by the Neanderthals’ appearance. They have a tremendously pronounced brow, but very little by way of a forehead. As E. H. Gombrich said of Neanderthals in his A Little History of the World, written for young audiences and first published in 1936, “Now, if all our thinking goes on behind our foreheads and these people didn’t have any foreheads, then perhaps they didn’t think as much as we do. Or at any rate, thinking may have been hard for them.”

  Gombrich’s delightful explanation might be right. It is indeed true that humans are perhaps the only species with foreheads, and we now know that those foreheads conceal a part of our brain known as the cortex. All mammals have a cortex but ours is unusually well developed. It is a region of our brain in which the connections among neurons are especially complicated and dense. Brain scientists link the cortex to imaginative, creative, symbolic, and other “high-level” thinking, and indeed we have seen that Homo sapiens was showing the first glimmerings of symbolism by 160,000 years ago. By sometime around 100,000 years ago, armed with our new brains, we became vastly more creative and inventive than our predecessors, and by 50,000 years ago we were building complex tools with more than one part, musical instruments, and bone tools with specialized functions. We had developed an aesthetic sense, as seen in portable art and jewelry, cave art and carvings, ceremonial burial and body adornment. Put it this way: the Stone Age didn’t end because people ran out of stones; it was replaced by a new age of inventiveness.

  Surprisingly, though, another feature of our intelligence might tell us that our inventiveness is not necessarily evidence of a great increase in raw intellectual capacity. As we have also seen, we appear to be the only species able to copy and imitate others’ ideas, an ability we called social learning. It makes cultures evolve rapidly by gathering together the talents of many individual brains, and making the contents of those brains available to everyone. But the irony is that social learning might also reduce the advantages to any one of us of being clever and imaginative, because your inventiveness can bring the same benefits to others as it does to you. This means there are opportunity costs to having a large brain if that large brain exists to be inventive. Why should I build and then support a large and hungry brain just to be inventive if I can get by copying your best ideas? I could use the energy needed to power my large brain for something else. And, if useful innovations are difficult to produce, the time we spend on creative but fruitless acts might be better spent gathering food, hunting, defending our territories, or repairing our shelters, and especially so if someone else can put in the effort of innovation for you.

  The thought that we might not be very inventive is one that most of us will dismiss outright. But when we think about it, we really are not all that good at being inventive. How do we generate new ideas? No one really has very much understanding of this question, but what we do know is that innovation is not just a matter of thinking hard until you get the answer. Imagine yourself 50,000 years ago trying to design a better spear. You want it to fly further than the ones you have, but also penetrate deeper into the animal you wish to hunt. What shape and weight should you give it? Most of us probably would not know the answers to these questions, so we would experiment by trying out lots of different options, and then choose the best. There would almost certainly be many false starts and wrong turns. Even today, our best engineers armed with centuries of accumulated knowledge can still be surprised by what they build. The Millennium Bridge is a stylish pedestrian suspension bridge that crosses the Thames in London near St. Paul’s Cathedral. It was opened on June 10, 2000, and was closed later the same day having already been nicknamed “the wobbly bridge.” Despite the best efforts of the engineers who designed it, the bridge swayed and twisted vertiginously as people walked across it.

  But these and other wrong turns won’t really have mattered too much in our past if a species has social learning. Like natural selection acting on genes, social learning will examine everyone’s attempts at some problem and act as a remarkably efficient sorting machine or “algorithm.” Someone making spears will have, even if just by chance, come up with a good design, and all of you trying to make better spears can copy it. This process even speeds itself up all on its own, as the pace of change of modern life attests. As more of you copy the good design, there will be more people using it, and so this design will become even more likely to be copied and improved upon. Over long periods of time, cultural evolution relying on social learning will be able to build objects of great complexity by a series of small incremental changes. It can do so even if at any given moment the proposals for how to improve the existing form are no better than random. There never have to be any great leaps of imagination or understanding, because just by chance one of these proposals will lead to an improvement, and social learning will find it. Engineers eventually solved the Millennium Bridge’s swaying—although not at the first attempt—and now everyone building bridges has access to this information.

  If you still cling to the view that humans must be highly inventive to have produced their great works of culture and technology, you would be in good company, even if mistaken company. The theologian and philosopher William Paley gave one of the more memorable arguments for the existence of a creator in his Natural Theology, written in 1802. Paley imagines himself out in the English countryside:

  In crossing a heath, suppose I pitched my foot against a stone, and were asked how the stone came to be there; I might possibly answer, that, for anything I knew to the contrary, it had lain there forever: nor would it perhaps be very easy to show the absurdity of this answer. But suppose I had found a watch upon the ground, and it should be inquired how the watch happened to be in that place; I should hardly think of the answer I had before given, that for anything I knew, the watch might have always been there. Yet why should not this answer serve for the watch as well as for the stone? Why is it not as admissible in the second case, as in the first? For this reason, and for no other, viz. that, when we come to inspect the watch, we perceive (what we could not discover in the stone) that its several parts are framed and put together for a purpose… . This mechanism being observed (it requires indeed an examination of the instrument, and perhaps some previous knowledge of the subject, to perceive and understand it; but being once, as we have said, observed and understood), the inference, we think, is inevitable, that the watch must have had a maker: that there
must have existed, at some time, and at some place or other, an artificer or artificers who formed it for the purpose which we find it actually to answer; who comprehended its construction, and designed its use… .

  Every indication of contrivance, every manifestation of design, which existed in the watch, exists in the works of nature; with the difference, on the side of nature, of being greater or more, and that in a degree which exceeds all computation. I mean that the contrivances of nature surpass the contrivances of art, in the complexity, subtility, and curiosity of the mechanism; and still more, if possible, do they go beyond them in number and variety.

  Paley’s assertion is that complex objects imply a maker because we can’t imagine them assembling themselves. His exposition is worth reading in full (the quotation above is just an excerpt of a longer passage), and not just for his elaborate description of the watch. Paley takes his reader on a gentle walk through the mind of someone confronted by watches, but also by marvelously complicated works of nature.

  By implication, Paley thought it implausible to believe that a complicated thing like a biological species could ever have arisen on its own. But his argument is often used to illustrate a misunderstanding of natural selection in the biological world. The last half century of evolutionary biology has told us that it is precisely the great sorting power of natural selection that means it can produce objects of vast complexity; it can do so without any designer; and it can do so despite the fact that the variety it has to act on at any given moment has been generated by a purely random process. Genes don’t know how to mutate to produce some desired outcome. In fact, the overwhelming majority of mutations are damaging to the organism that produces them. But all that is needed is that one of these mutations from among many leads to an improvement, and that the lucky individual who has it survives and passes it on to its offspring. Over time, individuals that inherit this fortuitous mutation will also tend to leave more offspring and eventually everyone will come to have the trait. This is natural selection, and if this process is repeated over thousands of generations, many small modifications can accumulate, one on top of another, to produce complex traits.