War: What is it good for?

by Ian Morris

This, Richard Wrangham suggests in his marvelous book Catching Fire, was as much of a turning point in the evolution of human violence as snacks were for bonobos. Anytime a chimpanzee catches a monkey or finds a particularly tasty breadfruit, Wrangham has observed in his many years in the rain forest, males materialize from all around, and fighting frequently breaks out. Even sweet-natured bonobos find it difficult to enjoy a morsel of monkey brain without being besieged by jostling beggars. It is hard, Wrangham observes, to imagine how either kind of ape could have cooked food without it all being stolen—in which case this adaptation would not have paid off and would not have spread through the population. This forces us to conclude, Wrangham suggests, that when cooking caught on, it did so as part of a package deal with another great change—the shift from living in large, sexually promiscuous troops (like chimpanzees or bonobos) to male-female pair-bonding.

  When chimpanzees and bonobos look for food, it is every ape for itself, with males and females active as both hunters and gatherers. Among modern human hunter-gatherers, though, men typically do nearly all the hunting and women nearly all the gathering, and they then share the food with each other and their offspring. The details vary according to where in the world people live, but in pretty much every hunter-gatherer society, woman’s work includes cooking and man’s work includes threatening or even attacking anyone trying to steal the couple’s food. This raises the costs of theft, changing the evolutionarily stable strategy. Families replace troops as the foundation of society, with elaborate rules of sharing and etiquette evolving to take care of the elderly, orphans, and others without their own home and hearth.

  These changes must have revolutionized protohuman intimacy. As our ancestors shifted from apelike sex lives to pair-bonding, proto-men’s best strategy for passing on their genes shifted too, from fighting their way to the front of the line and flooding proto-women with semen toward skill at courting and providing. If Homo ergaster males still had quarter-pound testicles, they would have been as much of an expensive luxury as enormous intestines. Proto-men still faced sperm competition from seducers and rapists, and could not get away with gonads as tiny as alpha-male gorillas’, but by modern times our testes had shrunk to just 1.5 ounces.

  Along with huge scrotums, proto-men also lost a rather revolting feature of bonobo and chimpanzee penises: a little spur on the side that works to scoop any old deposits of semen out of a partner’s vagina before inserting a new one. The fact that bonobos and chimpanzees both have these spurs strongly suggests that our last shared ancestor had them too and that protohumans lost their spurs because they no longer needed them. In their place, proto-men grew supersized phalluses. The average human erection is about six inches long, but chimpanzees and bonobos manage just three inches, and gorillas a meager inch and a quarter. Proto-women returned the compliment by growing breasts that look like mountains compared with the molehills on other apes.

  These anatomical peculiarities led Desmond Morris, a onetime keeper of primates at London Zoo, to conclude in his famous book The Naked Ape that humans are “the sexiest primate alive” (this was fifty years ago, before primatologists had discovered what bonobos get up to). Remarkably, zoologists cannot seem to agree on why human breasts and penises ballooned (“The inability of twentieth-century science to formulate an adequate Theory of Penis Length,” Jared Diamond dryly muses, is “a glaring failure”), but the obvious guess is that shifting from fighting for mates to courting them put a high priority on sending signals of sexual fitness, both to the opposite sex and to same-sex rivals. What better way to do that than by flaunting ostentatiously enormous organs?

  By 1.3 million years ago, the point at which bonobos and chimpanzees began diverging, protohumans had already evolved very, very far from other apes. Just how that affected strategies of trauma, though, remains controversial, because we currently have nowhere near enough fossil skeletons to get a sense of how many protohumans were bludgeoned, stabbed, and otherwise done to death. To date, only one body dating back more than a million years bears traces of lethal trauma, and even that is not a certain case of deliberate killing. Only in the last half-million years, when skeletons become much more common, do we find unambiguously fatal wounds.

  But given the similarities between the ways chimpanzees and modern humans fight, we can make some fairly secure speculations. In both populations, violence is overwhelmingly the preserve of young males, who are likely to be bigger, stronger, and angrier than females or old males. There is a saying that when you have a hammer, every problem looks like a nail, and to young male chimps and humans, wrapped in muscles and soaked in testosterone, many problems look like ones that force will solve. Primatologists tell us that males commit well over 90 percent of assaults among chimpanzees, and policemen tell us that the human statistics are very similar. Young males (human or chimpanzee) will fight over almost anything, with sex and prestige as the major flash points and material goods a rather distant third, and they are most likely to turn homicidal when they get together in gangs that outnumber their enemies.

  Evolutionists cannot at this point prove that humans and chimpanzees inherited the practice of lethal male gang violence from proto-Pan, but it is certainly the most economical conclusion. If that is right, we should probably also conclude that starting about 1.8 million years ago, pair-bonding made fighting less useful than courting as a mating strategy among Homo ergaster but did not reduce its value as a way to deal with rival communities of protohumans. Bonobos, by contrast, began evolving in an entirely different direction 1.3 million years ago, as female solidarity reduced the payoffs to male violence across the board. (Pair-bonding might actually have reduced the scope for bonobo-like group solidarity among protowomen.)

  As archaeologists excavate more skeletons, the details will become clearer, but the one thing we can already be certain about is that the protohumans’ new evolutionarily stable strategy was hugely successful. Homo went forth and multiplied as no ape had done before. Over the course of a thousand centuries, our ancestors spread across much of Africa, and a thousand centuries more of gradual extensions of their grazing ranges took them as far as what we now call England and Indonesia (the earliest skeleton with signs of violence in fact comes from Java). They moved into environments utterly different from the East African savanna, and, predictably, mutations flourished. Almost every year now brings an announcement that archaeologists or geneticists have discovered yet another new species of protohuman in Asia or Europe.

  By half a million years ago, one of these protohuman variants—known, after its original find spot in Germany, as Heidelberg Man—had evolved brains almost as big as ours, and over the next few hundred thousand years Neanderthals (also named after an original find spot in Germany) actually grew brains bigger than ours, albeit flatter, with some areas therefore less developed. One or both species might have communicated in ways we would call speech, and they definitely found new ways to kill, using resin and sinews taken from other animals to attach stone spearheads to wooden shafts.

  Archaeologists have found enough Neanderthal skeletons to know that they were very, very violent. At least two skulls bear healed traces of nonfatal stabbings. Stone spearheads are common on Neanderthal sites, and head and neck traumas even more so. The closest parallel to Neanderthal bone breakage patterns comes in fact from modern rodeo riders—but since there were no bucking broncos a hundred thousand years ago, we probably have to assume that Neanderthals got hurt fighting. Possibly all these fights were against their prey, but since their prey sometimes included other Neanderthals—the evidence of occasional cannibalism is overwhelming—it is hard not to suspect that the big-brained Neanderthals were the most violent of all the great apes. Clever, well armed, and extraordinarily strong (two leading archaeologists describe them as “combining [the physique] of a powerful wrestler with the endurance of a marathon runner”), by 100,000 B.C. they had extended their range from central Asia to the Atlantic.

  But then along came us.

/>   2.7 Pounds of Magic

  Inside your head is a little piece of magic. Nothing else in nature can compare with the 2.7 pounds of water, fat, blood, and protein pulsing away inside your skull, guzzling energy and fairly crackling with electricity. Four hundred million years in the making, this brain sets us apart from every other animal on earth and has changed everything about the place of force in our lives.

  Archaeologists and geneticists agree that this miracle of nature took on its fully modern form in Africa somewhere between 200,000 and 50,000 years ago. This was a time when new twigs were sprouting off the protohuman branch of the tree of life with particular vigor, perhaps because an extremely unstable climate kept changing the payoffs in the games of life and death.

  It was a wild ride: temperatures 200,000 years ago were distinctly cooler than today’s (on average, perhaps 3°F lower), but then, amid many wild zigs and zags, they tumbled into a genuine ice age. By 150,000 years ago, the world was 14°F colder than today. Mile-thick glaciers blanketed much of northern Asia, Europe, and America, tying up so much water that the sea level fell three hundred feet below what we are used to. No one could live on the glaciers, and the vast arid steppes around their edges, where winds howled and dust storms raged, were little better. Even near the equator, summers were short, water was scarce, and low levels of atmospheric carbon dioxide stunted plant growth.

  Humans that looked just like us, with high, domed skulls, flat faces, and small teeth, first walked the earth in these years. Excavated fossil remains and DNA studies both agree on this, suggesting that the first modern humans evolved in East Africa between 200,000 and 150,000 years ago. The odd thing about the earliest finds, though, is that while these great apes chipped stone tools, hunted and gathered, and fought and mated, little we find on their sites is very different from what we find on sites belonging to Neanderthals or other protohumans. Just why this is remains hotly debated, but it was not until after the world had warmed up for a few millennia and then crashed into another ice age that humans started acting like us as well as looking like us.

  Beginning between 100,000 and 70,000 years ago, odd things start turning up on archaeological sites. People were now decorating themselves, something previous protohumans did not do. They collected eggshells and spent hours chipping and grinding little disks out of them. Using just a pointed bone, they would drill a hole through the middle of each disk and string hundreds together in necklaces. They swapped these ornaments with each other, sometimes trading them across hundreds of miles.

  Protohumans were acting a lot less proto and a lot more human. They gathered ocher, a kind of iron ore, and used it to draw bold red lines on cave walls and probably on each other’s bodies. At Blombos Cave in South Africa someone even scratched simple geometric patterns onto a little stick of ocher seventy-five thousand years ago—making it not just the oldest known work of art but also a work of art used for making other works of art.

  People coaxed their fingers into producing tiny tools, lighter and subtler than anything seen before, and then used some of the tools as weapons. The oldest known carved bones include fishhooks, and among the oldest known stone bladelets (as archaeologists call the tiny tools) are arrowheads and javelin points. Bird and fish bones from caves along Africa’s southern shores show that people used these devices to kill prey that had previously been beyond their reach (remains of their shoulder and elbow joints suggest that Neanderthals, for all their fierceness, could not throw very well, let alone shoot arrows).

  Like Neanderthals, early Homo sapiens also occasionally ate their own kind, using stone blades to carve the flesh off meaty long bones and stone hammers to crack bones to extract marrow and the tastiest treat of all, the miraculous human brain. A steady trickle of bashed-in skulls uncovered by archaeologists strongly suggests that humans were killing each other, but we have to wait until thirty thousand years ago to find decisive evidence. This comes not from mutilated skeletons but from the famous paintings that Homo sapiens began leaving on cave walls in northern Spain and southern France. These are things of exquisite beauty. “None of us could paint like that,” Picasso is supposed to have said when he first saw them. “After Altamira, all is decadence.” However, some of them have a dark side too, showing unmistakable scenes of humans shooting each other with arrows.

  Archaeologists excavating sites between 100,000 and 50,000 years old occasionally find objects that look distinctly modern, such as jewelry or art, but sites younger than 50,000 years almost always include such artifacts. People were doing new things, finding new ways to do old things, and inventing multiple ways to do everything. From Cape Town to Cairo, pre-50,000-B.C. sites all look rather alike, with much the same kinds of finds used in much the same kinds of ways. Post-50,000-B.C. sites, however, vary wildly. By 30,000 B.C., the Nile Valley alone hosted half a dozen distinct regional styles of stone tools.

  Humans had invented culture, using their great, fast brains to weave webs of symbols that not only communicated complex ideas—Neanderthals and perhaps even Homo ergaster could do that—but also preserved them through time. Modern humans, unlike any other animal on earth, could change how they thought and lived in ways that accumulated, with one idea leading to another and mounting up across the generations.

  Culture is a product of the biological evolution of our big, fast brains, but culture itself also evolves. Biological evolution is driven by genetic mutations, with the mutations that work best replacing those that do not across thousands or even millions of years. Cultural evolution, however, moves much faster, because unlike the biological version, it is directed. People face problems, their little gray cells go to work, and ideas come out. Most ideas, like most genetic mutations, end up making little difference to the world, and some are downright harmful, but over time ideas that work well outcompete those that do not.

  Imagine, for instance, that you were a young hunter in the Nile Valley thirty thousand years ago. In my made-up game of death earlier in this chapter, I used “doves” as symbols for animals that never fight and “hawks” for those that always fight; here, I will use “sheep” to represent people who follow the herd and “goats” for those who don’t. Our young hunter is a goat, certain that he knows best, and he thinks up a new design for arrowheads. Let us say that his version has longer tangs, so that it will stay lodged in the flank of a wounded antelope better than the old style. To his astonishment, though, his sheepish associates pooh-pooh his idea, telling him that the ancestors didn’t need long tangs, so neither do we.

  Like fight and flight in the dove-and-hawk game, innovation and conservatism both have costs and benefits. Innovators pay a price: it takes time to learn to make new arrowheads and to use them properly (costing, let us say, 10 points), and—perhaps more seriously—going against the way things have always been done might lose them respect (–20 points). Other men might not want to cooperate on hunts with someone so quirky, in which case the goatish inventor might actually end up with less meat, despite having better technology (another –10 points). In the end, he might just let the whole thing drop.

  Unless, that is, the gains outweigh the losses. If his arrowheads really do produce more kills, he not only gains weight by eating more (say, +20 points) but also can gain prestige by sharing antelope steaks generously (+25 points). Such a successful man might get more sex (a further +10 points), which will put the balance firmly in the black (at +15 points). Over several generations he might spread his ingenious, goatish genes through the little hunter-gatherer group; but cultural change will overtake biological change long before that happens, because the other men in the band will simply copy his arrowheads. The inventor’s tally of points and luck with the ladies will then decline, but perhaps not quite back to zero, because now everyone is eating better—unless, of course, the hunters’ new technology is so effective that it kills off all the antelopes, setting off new chains of consequences …

  Like the dove-and-hawk game, this is fun to play. We can make the story bra
nch off in all kinds of directions, because even small changes in the payoffs produce big changes in the results. But the point, as with the earlier game, is that in real life the sheep-and-goat game is played over and over, with different results each time. If the costs of going against tradition are high in the inventor’s band, the arrowhead will not catch on, but if it really is a better arrowhead, people in other bands will also think of it, and before long it will catch on somewhere else. Goatish bands might then out-hunt sheepish ones, forcing the latter either to switch arrowheads after all, or change their diet, or fight the innovators—or in an uncaged landscape they could just move away.

  Culture wars of this kind are uniquely human. Although some other animals can be said to have cultures (particularly chimpanzees, among whom each community does things slightly differently from its neighbors), none seem to be capable of cumulative cultural change. The evolutionary consequences of culture have been a bit like those of the rise of sexual reproduction 1.5 billion years ago: where sex sped up genetic mutation, culture sped up innovation. Both mechanisms vastly increased the diversity of outcomes, allowing cells or humans to cooperate and compete on a bigger scale.

  Armed with brains powerful enough for cultural evolution, modern humans conquered the world. A few Homo sapiens had drifted out of Africa just before 100,000 years ago, when culture was still a fragile flower, and perhaps because of this these early emigrants only got as far as what we now call Israel and Arabia. There they lived alongside Neanderthals, although not necessarily happily: the oldest known fatality from a spear thrust, around 100,000 years ago, was one of these pioneers. But a second wave, which broke out of Africa about 70,000 years ago, took the full package of modern human behavior with it and spread across the planet fifty times as fast as the protohumans who had left Africa nearly 1.6 million years earlier.

  Culture gave the new migrants huge advantages over protohumans. When modern humans arrived in Siberia thirty thousand years ago, for instance, it was even colder than it is now. But unlike other animals, they did not have to wait millennia while their genes evolved toward hairiness to keep them warm. Instead, they invented bone needles and gut threads and sewed fitted clothes. There might have been conservatives who preferred traditional, ill-fitting skins to this new look, but the first winter either changed their minds or killed them.