She Has Her Mother's Laugh: The Powers, Perversions, and Potential of Heredity (61 page)

Before spraying a bubble net, the whale first slapped the water with the underside of its tail. In the years that followed, whale observers recorded other animals in the gulf slapping the water as well. The proportion of whales performing this so-called lobtail feeding increased in fits and starts for decades.

In 2013,
Luke Rendell of the University of St. Andrews, Scotland, and his colleagues mapped the records of lobtail feeding onto the social network of the whales. Humpback whales have a loose social organization, coming together into small groups to feed and mate. Rendell found that whales typically didn't just start spontaneously lobtail feeding on their own. Spending time with a proficient lobtailer made them much more likely to try out the method for themselves.

Rendell argued that this new tradition became entrenched in the Gulf of Maine for the same reason that blue tits started drinking cream: We changed their food supply. The whales fed on herring until the stocks collapsed due to human overfishing. They then switched to sand lances for their prey. It's possible that a whale discovered that smacking the water stunned the sand lances, preventing them from escaping whale attacks.

When scientists can't observe a new tradition take hold in the wild—which is most of the time—they can get some clues to its history by simply comparing the populations that make up a species. The chimpanzees that live in the Kibale Forest in Uganda, for example, use sticks to extract honey from logs. In the Budongo Forest, not far away, chimpanzees get honey in a
different way: They chew up leaves and then use them as a sponge. Rather than being some instinct shared by all chimpanzees, these behaviors were probably invented by some innovative chimpanzees and then became local traditions.

The traditions of chimpanzees are especially important to understanding human culture because they're our closest living relatives. Primatologists have cataloged dozens of traditions among these apes, many found only in some populations but not others. Any one population may have a unique combination of traditions—for getting food, for using plants as medicine, for grooming each other, for making calls to other chimpanzees, for performing courtship rituals. Andrew Whiten, an expert on animal traditions at the University of St. Andrews, has argued that these bundles of traditions should be treated as cultures. If Whiten is right, that means that our cultural history reaches back at least seven million years, to our common ancestor with chimpanzees.

Only after our ancestors split off from other apes did truly human culture emerge. One way to study its rise is to run experiments in which humans and other species perform the same task, and then see how they do it differently.

At the University of St. Andrews, a graduate student named
Lewis Dean designed one such test. He created a “puzzle box” that dispensed rewards with the right combination of actions. When monkeys and chimpanzees tried to solve the box, they were rewarded with fruit; three- and four-year-old children got shiny stickers.

To get the rewards, the subjects had to uncover three hidden chutes. They could reveal the first chute by sliding a door to one side. Once they learned how to do this, they could learn how to push a button on the box that let them slide the door farther, revealing the second chute. And if they then turned a dial in the right direction, they could slide the door farther still, revealing the third chute.

Dean showed the box to two groups of capuchin monkeys. To get them
started, he slid the door open to demonstrate how to get the first reward, but he then left them to their own devices after that. All told, each group of monkeys played with the puzzle box for fifty-three hours. And yet, after all that time, only two of the monkeys learned how to get the second reward. None got the third. When Dean put the puzzle box in front of chimpanzees, they fared almost as poorly. After thirty hours, only four chimpanzees got the second reward, and only one got the third.

The children, who were three or four years old, did far better. Dean showed the box to eight groups, each consisting of up to five children. In five of the groups, at least two children figured out how to open up the third chute. Many others managed to get the second one. And they made all this progress in just two and a half hours.

The children did so well because they—unlike the primates—could go beyond simply solving isolated problems. They could accumulate knowledge, and they did so as a group. When some of the children figured out how to reveal the first chute, the other children could learn it from them. And then the other children could use their own insights to add a new step in the procedure, revealing the second chute.

Many anthropologists now argue that this so-called
cumulative culture is a hallmark of our species. The cultural practices that chimpanzees carry out are simple, requiring just a few steps to complete. They have never shown any capacity to learn a practice and then build on it. Humans, by contrast, are constantly adding on to the practices they've learned, creating complex new forms of culture. They can build up elaborate recipes for nardoo, modify canoes until they are able to cross the Pacific, and turn wooden guitars into electric ones.

Dean's experiment illuminates a few of the crucial traits that make cumulative culture possible. Friendliness matters, for one thing. When Dean gave the puzzle box to the primates, they competed over it rather than cooperating. The ones that figured out how to get fruit out of a chute always gobbled it up, never sharing it with others. The children, on the other hand, were more comfortable in each other's company. Some of them even spontaneously gave the stickers they got out of the puzzle box to others
who didn't. The friendlier children were, Dean found, the better they did on his test.

A number of other studies have come to a similar conclusion: We humans have evolved more tolerance for each other than other species. That gives us more opportunity to learn from one another. And that extra social learning may be crucial for making culture cumulative.

The children in Dean's experiments stood apart from the chimpanzees and monkeys in a second way: They sometimes taught each other. When children figured out how to open a new chute, they sometimes demonstrated to the others how to do it. Dean never witnessed a single lesson taught by the chimpanzees or the capuchins.

Anthropologists were slow to recognize how important teaching has been to our species. In the mid-1900s, Margaret Mead and other experts claimed that teaching was merely
a peculiar feature of Western societies, a cultural penchant for herding children into schools. In other cultures, children were supposedly left to their own devices, to learn for themselves. In recent years, though, many anthropologists have changed their minds, in part because they've reconsidered what it really means to teach. Teaching doesn't have to happen in a lecture hall or run on a semester schedule. At its essence, teaching is a behavior that one person uses to help another person learn a skill or acquire a piece of information. And by that definition, teaching appears to be common in human societies.

In the rain forests of central Africa, for example, Barry Hewlett, an anthropologist at the University of British Columbia, found evidence for teaching among the Aka, a group of pygmy hunter-gatherers. The Aka don't run schools, and they don't even have a word for
teach
. And yet Hewlett found that adults are constantly teaching children. The lessons happen in brief bouts, some as short as a few seconds. Sometimes the adults don't utter a word. But they still manage to convey crucial lessons to their young children, such as how to build a fire, how to use a machete, and how to find yams and dig them out of the ground.

Once researchers settled on their new definition of
teaching
, they wondered if other species teach as well. They have found only a few cases where
the answer seems to be yes.
Meerkats are one. In the deserts of southern Africa, they hunt many species of prey—some of which, like scorpions, are dangerous. Killing and eating a scorpion without getting fatally stung is a difficult skill to learn. Adult meerkats make it easier for pups by letting them practice safely. They start by bringing dead scorpions to their young. When the pups get older, the adults only wound the scorpions, and also make sure to rip off their stingers. Later, when the pups have developed some skill at handling live scorpions, their parents don't wound their prey as badly. At the end of the lessons, the pups are ready to kill live scorpions on their own.

As impressive as this teaching may be, meerkats appear to be an exception among animals rather than the rule. Even among our closest relative, animal teachers appear to be rare. In 2016, researchers from Washington State University reported that they had spotted
chimpanzee teachers in a forest in the Republic of Congo. The adult chimpanzees there have a cultural practice of fashioning sticks into tools for fishing termites. Sometimes the adults will hand their tools to a young chimpanzee so that it can give it a try. Given the decades that scientists have been watching chimpanzees in the wild and in zoos, it's remarkable that the Washington State University team made the first observation of any behavior that might be called teaching. Teaching would make a tremendous difference to the well-being of chimpanzees. Cracking nuts with stones is so difficult that young chimpanzees can take as long as
four years to master the skill. Yet in all that time, no one has seen an adult chimpanzee offer some guidance.

For humans, by contrast, teaching comes easily—so easily that children will spontaneously teach each other about games and toys. This tendency (which goes by the technical term
natural pedagogy
) may be rare in the animal kingdom because it demands a lot from teachers and students alike. Successful teachers have to be able to gauge what their students do and don't know, which demands an ability to get inside their heads. Teachers also need to communicate information clearly so that their students will be likely to learn something new. If teachers fail at any these challenges,
all their efforts are wasted.

What's more, the best teachers in the world can't teach students unable to absorb their lessons. Humans seem to have evolved to be especially good students. One of the most important adaptations we've evolved—and one of the strangest—is what Derek Lyons was testing by studying Charlotte:
extreme imitation.

Children are willing to imitate teachers even when they should know better. In a species like ours, in which teachers transmit important lessons, extreme imitation is a smart strategy. Children don't have to struggle to reinvent all of human culture from scratch. Dean's experiment gives a glimpse at imitation's value. The children who tried solving his puzzle box imitated each other fairly often, and the children who imitated the most got the most rewards.

There are certainly risks to imitating someone rather than wondering about each step along the way. If children end up imitating people who don't know what they're doing, they'll reproduce failure. But humans appear to have evolved some defenses against this sort of mistake. If children can choose whom to direct their attention, they'll tend to focus on adults who appear to be
trustworthy experts. “
The theory of natural pedagogy,” the British psychologist Cecilia Heyes says, “suggests that blind trust is at least as important as smart thinking.”

These ingredients for cumulative culture must have emerged after our ancestors split off from the ancestors of chimpanzees some seven million years ago. We don't have a lot of evidence to narrow that window and pin down the precise timing of when we started teaching, imitating to the extreme, and the like. We have to rely mostly on the material products of cumulative culture.

You can tell that living humans have cumulative culture by their stuff: If you haul together all the man-made objects in an Aka camp, they'd be different from what you'd collect from a Greenland Inuit settlement or a middle-class house in Nebraska. And if you collect objects from a single place stretching over a span of thousands of years—say, pottery from Egypt—you'll find one set of objects morphing into new sets. But if you try to reach back millions of years, the evidence gets scarce.

The technological record of humans and their ancestors reaches back
3.3 million years. In 2015, researchers in Kenya discovered small chipped stones that could be used to chop, hammer, or cut. It's possible that hominins used these tools to scavenge meat from dead carcasses. A million years later, hominins in Tanzania were still making these tools. But the shape of these pieces of rock—
known as Oldowan tools—reveals a change of thought. The hominins who made them understood how to knock off a sharp flake from a rock while leaving the rock intact enough to yield another flake. They could thus produce a number of tools of about the same size and shape, all made from a single rock. This skill probably had to be taught. Young hominins likely needed a teacher to demonstrate how to knock off flakes, to communicate its goal, and to help them improve their technique.

It wasn't until about 1.8 million years ago that new kinds of technology emerged. The most striking of the next generation of tools was a large, teardrop-shaped hand ax. The species
Homo erectus
carried these hand axes to Asia and Europe and kept making them for over a million years. They made the axes from flint, basalt, quartz, and even obsidian. But the overall shape stayed pretty much the same.

These hand axes hint that
Homo erectus
was approaching our level of cultural prowess. The tools may look crude to our modern eye, but a twenty-first-century human would be hard-pressed to make them from scratch. First you'd need to find the right supply of rocks (I'm guessing you don't know where the nearest vein of obsidian is to be found). And then you'd need to strike one rock with another many times over to craft the proper shape. Paleoanthropologists sometimes run experiments to see how much prowess is required for making hand axes. They give people a finished model and some rocks they can thwack together.
Their subjects always fail. It takes years for aficionados of the Pleistocene to learn how to make a good hand ax.