The Social Leap

William von Hippel

• Publisher: Harper
• Year: 2018
• ISBN:
  9780062740410
• Topic: Psychology
• Subtopic: Social Psychology
• Index: Psychology

In the compelling popular science tradition of Sapiens and Guns, Germs, and Steel, a groundbreaking and eye-opening exploration that applies evolutionary science to provide a new perspective on human psychology, revealing how major challenges from our past have shaped some of the most fundamental aspects of our being.

The most fundamental aspects of our lives—from leadership and innovation to aggression and happiness—were permanently altered by the "social leap" our ancestors made from the rainforest to the savannah. Their struggle to survive on the open grasslands required a shift from individualism to a new form of collectivism, which forever altered the way our mind works. It changed the way we fight and our proclivity to make peace, it changed the way we lead and the way we follow, it made us innovative but not inventive, it created a new kind of social intelligence, and it led to new sources of life satisfaction.

In The Social Leap, William von Hippel lays out this revolutionary hypothesis, tracing human development through three critical evolutionary inflection points to explain how events in our distant past shape our lives today. From the mundane, such as why we exaggerate, to the surprising, such as why we believe our own lies and why fame and fortune are as likely to bring misery as happiness, the implications are far reaching and extraordinary.

Blending anthropology, biology, history, and psychology with evolutionary science, The Social Leap is a fresh and provocative look at our species that provides new clues about who we are, what makes us happy, and how to use this knowledge to improve our lives.

Part I

How We Became Who We Are

1

Expelled from Eden

You and I are descendants of chimplike creatures^* who left the rainforest and moved to the savannah six or seven million years ago. On first glance it would seem like an odd decision for our ancestors to leave the trees, as there were virtually no predators that could hunt them successfully when they were in the forest canopy. Even superb tree climbers such as leopards don’t attack chimps in trees, as chimps are simply too fast and too dangerous when they are in their element. On the ground, however, chimps are easy prey. They are ungainly on two legs, comparatively slow on all four, and their small size makes them an easy meal for large cats such as lions, leopards, or the saber-toothed tigers that once roamed East Africa.

So why leave the trees? What compelled our ancestors to trade the safety and sheer exuberance of life in the canopy for a slow and clumsy existence on the ground? There is vigorous scientific debate on this question, but one widely endorsed theory is an updated version of the “savannah hypothesis.” This hypothesis was proposed by Ray Dart in 1925, when he published the discovery of Australopithecus africanus, or “the man-ape of South Africa.” After noting that humans were unlikely to have evolved in tropical forests because life there was too easy, Dart wrote, “For the production of man a different apprenticeship was needed to sharpen the wits and quicken the higher manifestations of the intellect—a more open veldt country where competition was keener between swiftness and stealth, and where adroitness of thinking and movement played a preponderating role in the preservation of the species.”

Dart was right that we evolved in the savannah, but in 1925 he had no idea what forces put us there. We now believe that tectonic activity along the East African Rift Valley is what split us from our chimpish ancestors. All the earth’s surfaces, including the landmasses that make up the continents and the bottoms of the oceans, sit on tectonic plates. These plates float around on an underlying mantle, which emerges as a viscous liquid when it flows from a volcano but is under so much pressure below the earth’s crust that it is more like pliable road tar. The heat emanating from the earth’s core creates incredibly slow but strong currents in the mantle, and these currents carry the plates around with them. Sometimes these plates ram into each other in super slo-mo, as is the case with India smashing into Asia, a by-product of which is the Himalayas (which continue to rise a few centimeters each year). Sometimes these plates tear apart and move away from one another. In Africa, the east side of the continent is slowly unzipping from the rest, starting at the Red Sea, in the north, and ending at the coast of Mozambique, in the south.

The tectonic activity along this geographic zipper created the East African Rift Valley and slowly and sporadically raised vast portions of Ethiopia, Kenya, and Tanzania to an elevated plateau. These changes in topography led to localized changes in climate, with the rainforests on the east side of the Rift Valley drying out one by one, to be replaced by savannah. So it turns out that we didn’t leave the trees after all—the trees left us.

Because our chimpish ancestors were so impressive in the trees and so unimpressive on the ground, the gradual replacement of the rainforest with savannah meant that they had to find a new way to make a living. The fruits, berries, and leaf buds they were accustomed to eating receded along with the trees, their opportunities to hunt for meat were greatly diminished by their slow speed on the ground, and, to top it off, enormous predators prowled the grasslands. So how did our ancestors respond to this double whammy of disappearing food and newly dangerous predators? No doubt many of our would-be ancestors perished, but some of them survived and eventually began to thrive, and their story is our own.

The Dik-Dik/Baboon Strategy

Our chimpish ancestors are not the only tree dwellers who ever tried out life on the ground, so scientists often look to the behavior of other species to see how chimps might have adapted to the grasslands. One analogue can be found in baboons. Although baboons are monkeys and not apes (and hence not as clever as chimps), they resemble chimps in many ways, and several baboon species reside on the African savannah. Savannah baboons live in large groups, which gives them the advantages of many eyes to watch for predators and many teeth with which to defend themselves. The “baboon solution” to savannah life isn’t a terrible one, as evidenced by the fact that there are still plenty of baboons, but it is stressful and fraught with danger. Baboons often meet an abrupt end in the mouth of a hungry lion or leopard.

In their confrontations with predators, baboons depend heavily on their massive incisors, which are larger than those of a chimp even though baboons themselves are smaller. If our chimpish ancestors had “decided” that biting was the answer to their savannah dilemma, our faces would likely be more doglike than they are today, with a protuberant jaw and much larger teeth. Our tiny jaws and pathetic canines indicate that the baboon solution doesn’t appear to have suited our ancestors, who took a different approach to life on the plains. Indeed, this decision was already evident by the time we had evolved into Ray Dart’s Australopithecus, whose jaw and teeth were halfway between a chimp’s and our own.

Because chimps are brainier than baboons, they take longer to reach adulthood, and their slower maturation rate means they demand more maternal care. As a consequence, chimps have an older age of initial reproduction and a lower rate of reproduction than baboons. This slower reproduction would have put our ancestors at a greater risk of extinction if they had been picked off at the same frequency as baboons. For this reason, our chimpish ancestors who survived this evolutionary pressure cooker were probably the ones who did their utmost to escape the notice of lions, saber-toothed tigers, and other predators rather than taking a more confrontational approach.

Indeed, hiding is the primary survival strategy for many herbivores. Consider the dik-dik, an antelope about the size of a house cat that also lives on the East African savannah. By virtue of their diminutive size, dik-diks have no defense against any predator larger than a poodle, so they spend their lives hiding. They are impressively quick and agile when chased, but not fast enough to survive being hunted on the open grasslands. As such, dik-diks blend into their surroundings, stay on the lookout for predators, and never stray far from heavy bush.

Our chimpish ancestors weren’t as quick as dik-diks, but they could climb trees. It’s likely they spent their day hiding, watching for predators, and scrambling up nearby trees for safety. When modern chimps are in the savannah, they adopt this sort of combined dik-dik/baboon approach, clustering together more than chimps do in the rainforest and cautiously avoiding open areas where there are no trees available for a ready escape. Perhaps even more interesting, savannah chimps exhibit two other unique behaviors: they fashion crude spears out of tree branches, which they use to poke into tree hollows to skewer and retrieve the monkeys hiding inside, and they are more likely than rainforest chimps to share with one another. Both these behaviors mimic changes shown by our ancestors after they left the forest (more on this later).

These data from savannah chimps and baboons suggest that greater watchfulness would have allowed our ancestors to eke out a living on the savannah, and probably played an important role in their survival for the first few million years after the disappearance of the forest. Unlike baboons and dik-diks, however, our ancestors were not content with this modicum of success. The savannah brought with it new opportunities for a clever ape whose hands were no longer required for locomotion. Change didn’t come overnight, but across the ensuing three million years, numerous adaptations to our minds and bodies suggest that we found entirely new ways to protect ourselves on the grasslands.

Throwing Rocks at Lions

What would you do if you were attacked by an animal that was too strong, too ferocious, and too fast for you to flee or fight off with your bare hands? In my case, it doesn’t take much imagination to answer this question. I grew up in a neighborhood that was inattentive to leash laws, and my friends and I were often chased by a German shepherd and Doberman pinscher that lived on our street. Even though I was a scrawny kid, and these dogs would still intimidate me today, by the age of seven or eight I had become pretty good at defending myself by throwing stones. Especially if my brothers or friends were with me, all we had to do was bend over to gather rocks, and the dogs running toward us would pull an immediate about-face. When I was alone, I took off for the nearest fence or tree, because I couldn’t throw rocks fast enough to do the job, but the addition of even one other person meant we could stand our ground.

These experiences suggest how our ancestors might have responded to the threat of predation on the savannah: by throwing stones, particularly if they could band together and throw lots of them. We can’t look back in time to see if that’s what they did, but we can look at differences between our bodies and theirs to see if this strategy is plausible. So, what does the evidence show?

Sure enough, a number of changes in the fossil record support the stone-throwing hypothesis. Most of these changes can be found at least partially in our ancestor Australopithecus afarensis (aka Lucy, who roamed East Africa three and a half million years ago and was a predecessor of Ray Dart’s Australopithecus africanus). Lucy wasn’t much brighter than a chimp, judging by the size of her brain, but she appears to have devised new ways to deal with predators beyond hiding and hoping not to be noticed. Compared to a chimpanzee, she had a more mobile hand and wrist, more flexibility in her upper arm, a more horizontally oriented shoulder, and more space between her hip and the bottom of her rib cage. This changing constellation of traits was likely a product of the fact that she was bipedal (she walked upright), a habit her ancestors evolved on the savannah. These new traits were also incredibly useful for throwing.

When you watch people toss a ball back and forth at the beach, you may get the impression that throwing is mostly a function of arm and shoulder muscles. If you want to learn to throw with power and accuracy, however, you need to watch baseball players, quarterbacks, or hunter-gatherers. Among experienced throwers, arms and shoulders are just a small part of the equation. Power throwing begins by stepping forward with the opposite-side leg (e.g., a left foot step for a right-hander), progresses through rotation of the hips, followed by rotation of the torso and then shoulders, and finally the elbow and wrist follow through.

These sequential motions take advantage of the fact that the combined forward and rotational forces of the body stretch the ligaments, tendons, and muscles of the arm and shoulder, which accelerate the arm forward at the very end of the throw, like the snapping of a rubber band. Chimps are stronger than we are, but they can’t generate this sort of elastic energy when they throw because their joints aren’t flexible enough and their muscles don’t line up in the right way. These changes to the hips, shoulders, arms, wrists, and hands are what made Lucy and her fellow Australopithecines much better stone throwers. These same changes also supported excellent clubbing,^* which would have been useful whenever throwing failed to do the job.

Driving off a Doberman with rocks is one thing; driving off lions and saber-toothed tigers is another challenge altogether, especially when you weigh between sixty and a hundred pounds and stand three and a half to five feet tall, as Australopithecines did.^* Nonetheless, throwing can be incredibly effective if you practice a lot. I first had my nose rubbed in this fact when I was in my late twenties and visited the Ohio State Fair with my girlfriend. One of the stalls had a pitching net with a radar gun, and I decided to impress her with my athletic prowess. I was pretty pleased with my fifty-mile-per-hour throws, and she seemed suitably awed—until a gangly twelve-year-old set up shop next to me. Without so much as breaking a sweat, this prepubescent eighty-five-pounder easily hurled ball after ball at sixty-plus miles per hour. Not wanting to lose this manly contest to a human twig, I threw my last ball as hard as I possibly could and was rewarded with a wildly inaccurate fifty-five-mile-per-hour pitch and excruciating pain in my elbow and shoulder. My girlfriend consoled me by suggesting that throwing was more practice than power—I think this was the moment when I first knew I wanted to marry her—and of course she was right.

Keeping in mind that practice makes perfect, we see that the throwing hypothesis is more plausible, particularly if throwing is taken up by an entire group. Consistent with this possibility, the historical record also indicates that throwing can be remarkably effective. There are numerous descriptions of encounters between European explorers and indigenous populations in which conflict ensued and the indigenous population was armed only with stones. The European explorers typically relied on guns and armor, but they often lost these skirmishes, sometimes badly. Consider these three historical accounts that anthropologist Barbara Isaac dug up for her wonderful article “Throwing and Human Evolution.”

In hardly any time at all they had so badly beaten us that they had driven us back into shelter with heads bloodied, arms and legs broken by blows from stones: because they know of no other weaponry, and believe me that they throw and wield a stone considerably more skillfully than a Christian; it seems like the bolt of a crossbow when they throw it.

—Jean de Béthencourt, 1482

The enormous stones hurled by the savages maimed one or other of our people at every moment . . . a shower of stones, so much the more difficult to avoid, as being thrown with uncommon force and address, they produced almost the same effect as our bullets, and had the advantage of succeeding one another with greater rapidity.

—Jean-François de Galoup de La Pérouse, 1799

Many a time, before the character of the natives was known, has an armed soldier been killed by a totally unarmed Australian. The man has fired at the native, who, by dodging about has prevented the enemy from taking correct aim, and then has been simply cut to pieces by a shower of stones, picked up and hurled with a force and precision that must be seen to be believed . . . the Australian will hurl one after the other with such rapidity that they seem to be poured from some machine; and as he throws them he leaps from side to side so as to make the missiles converge from different directions upon the unfortunate object of his aim.

—John Wood, 1870

These accounts highlight the potential deadliness of collective stone throwing, but they also highlight a crucial point: cooperation is the key to making this strategy a success with large animals such as lions and leopards.

The Psychology of Collective Action

Chimps are more likely to compete with one another than they are to cooperate, and thus it would have been difficult for our chimplike distant ancestors to act collectively to drive off large predators. A lone Australopithecus afarensis throwing stones (perhaps while other members of its group ran away) would have ended up in the belly of a slightly bruised predator, but many Australopithecines throwing stones could probably have driven off hyenas, saber-toothed tigers, and even lions. It was this need for collective action that brought about the most important psychological change that enabled us to thrive, rather than just survive, on the savannah: the capacity and desire to work together.

Modern chimpanzees cooperate loosely with one another when they hunt as a group and when they attack other chimps as a group, but their fundamental orientation toward group members who are not kin or close friends is competitive. Thus, it is likely that the first hundred, thousand, or even million times our chimpish ancestors were sneaking across the grasslands, they scattered for the nearest trees at the first sign of attack. But somewhere along the line, our ancestors banded together in their collective defense, at which point they all stood a better chance of survival.

Individuals in groups who learned to work cooperatively in this manner were at an enormous advantage, and would have easily outbred individuals in groups co...