Cultural transmission makes animals flexible, but vulnerable

Just a few decades ago, even most biologists would have readily agreed that culture is a quintessentially human feature.

Sure, they already knew there were dialects in birdsong, and good evidence that many birds largely learned these regional songs by copying other birds. They knew that some enterprising European songbirds called tits had learned how to open milk bottles by watching one another. Scientists had even reported that the practice of washing sweet potatoes in seawater had spread among the members of a Japanese colony of macaque monkeys.

But these and similar behavioral differences between populations — ones that couldn’t easily be explained by differences in their genes or environment — seemed limited in scope. Compare that with human culture, which creates variation in nearly everything we do. 

In recent decades, however, scientists have learned that culture plays a much more pervasive role in the lives of nonhuman animals than anyone had imagined. “The whole field has absolutely exploded in discoveries in the present century,” says primatologist Andrew Whiten of the University of St. Andrews, Scotland, the author of a 2019 overview of cultural evolution in animals in the Annual Review of Ecology, Evolution, and Systematics. 

Whiten was one of the pioneers of the surge in animal culture research. In 1999, he oversaw an analysis in which primatologists published their findings from nearly four decades of studying wild chimpanzees, our closest living relatives. “We could show chimpanzees have multiple traditions affecting all different aspects of their lives,” he says — from foraging to tool use to courtship. Similar findings followed for several other apes and monkeys.

But Whiten felt he needed to do more to demonstrate that these traditions truly came about by learning from others, so he decided to introduce a new tradition himself. Working with two captive groups of chimpanzees, he taught a single chimp in each group how to get a treat from a box. Crucially, they were each taught a different method. 

The ability to open the box spread within each group. But though both methods were equally effective, chimpanzees almost exclusively picked up the method used by the first trained animal in their group. 

This was an artificial setup in captivity, though. Whiten and colleagues wanted to witness the same thing in the wild — a difficult proposition, because wild chimpanzees are wary of people and disinclined to engage with items that are handed to them. So the team turned to vervet monkeys, teaching different wild groups to avoid grains of corn of a certain artificial color by giving the grains a bitter taste, until group members had learned to avoid them. Then the bitter flavor was removed. 

Once again, they could show that monkeys were clearly learning from one another: When individuals moved into another group, they would change their preference to avoid the grains the locals were avoiding, and prefer the ones they had previously avoided themselves. Evidently, these monkeys trusted the locals to do the right thing, even though all grains were now perfectly edible. 

Whiten’s approach has itself spread rapidly — among his colleagues. By now, “transmission chain” studies demonstrating that individuals learn from one another have been done in at least 20 different species, including in rodents, birds and fish. Even some insects have been shown to learn from others: Bumblebees are attracted to flowers that are popular with others of their species, and can even learn how to pull a string by watching others perform the same feat. And female fruit flies have been shown to prefer artificially colored partners they had seen mating with others. 

Of course, says Whiten, it remains to be shown whether these lab discoveries mean insects also have a capacity for what he would consider true culture, maintaining multiple traditions in the wild across generations. But he believes the finding that so many animals can learn from others is fundamentally important for our understanding of biology. “What we’ve got here,” he says, “is a second inheritance system, built on top of the genetic one that is shared by all life, that operates in some interestingly different ways.” 

In a hurry? Use culture 

When animals acquire their behavioral repertoire by watching others instead of through their own exploration or from the genetic code they inherit from their parents, that can have distinct benefits. For one thing, it is often faster.

Genetic evolution only works when successful individuals survive and reproduce, thus passing on the genes coding for their behavioral tendencies to the next generation. If promising new behaviors can simply be copied from others, that can speed things up a lot.

In addition, and in contrast to genetic inheritance, animals can adopt new behaviors not only from their parents but from any individual that lets them get close enough to watch — provided they are sufficiently clever to figure out and remember what’s going on.

This may not be so important if a creature lives in a place that remains the same from generation to generation. But when conditions change rapidly — as they are doing today due to climate change and other human influences on nature — genetic inheritance can be frustratingly slow.

The variation that natural selection has to work with is the result of processes that introduce almost entirely random changes in our genetic material. Animals behaving in ways that are well-suited to their environment will likely produce more offspring, which will have a greater chance of inheriting the same tendencies from their parents’ genes. Improvements on the trait will come through repeated rounds of this process. 

A species that can learn from others, on the other hand, does not need multiple generations to adapt. Individuals can opt to learn from those they have seen to be successful, tweak the behavior on their own, then pass on the new and improved version to their offspring — all things genetic inheritance can’t do.

Great tits — of milk-bottle-opening fame — are an excellent example of the exciting possibilities that emerge when you can learn also from animals that aren’t your parents, says behavioral ecologist Lucy Aplin of the Max Planck Institute of Animal Behavior in Germany. After leaving the nest, chicks spend only about 10 to 30 days with their parents, and during this time, “they learn how to find insects like caterpillars, their favorite summer food,” she says. “But by the time winter comes along, their only option is to learn from others.” 

In winter, the birds gather in flocks, providing a chance to learn how to extract food from tricky places, this species’ specialty. In a series of experiments, Aplin and her colleagues were able to show that, like the chimpanzees, great tits will learn from other tits that already know how to open a box rather than figure out equally effective methods by themselves.

A follow-up study revealed some limits, however. When the researchers made the task more complicated by introducing extra steps, the birds could no longer copy the task in its entirety from others but had to learn the steps separately and recombine them on their own. This could be because tits, though fast learners, aren’t very tolerant of each other, says Aplin. Any bird lingering too long near another will be chased off.

“This significantly reduces the opportunity for learning complex tasks,” says Aplin. She expects these limitations mean that more intricate tricks may usually be mastered only by a handful of birds and will eventually be lost from the flock. So even though tits do get better at new tasks, and can combine what they’ve learned, they soon reach a plateau.

This is a crucial difference with apes and especially humans, who are often much more tolerant and spend years learning from others. Because human knowledge is so faithfully transmitted, we have been able to build on the innovations of earlier generations to create things no one person could come up with individually. Whether other animals have any such “cumulative” culture remains controversial. But evidence is building that some species can indeed refine or recombine behaviors they’ve learned from others. 

A series of studies by behavioral biologist Dora Biro and colleagues at the University of Oxford, England, found evidence for this in homing pigeons, which will dependably fly home as soon as they are released. In experiments, the birds gradually shortened their routes as they repeated them. But interestingly, duos of birds were better at this — on the surprising condition that one of the birds was occasionally swapped out for one that had never flown the route before.

Over the first 12 flights, all duos improved. Yet duos of birds that flew an additional four rounds of 12 flights each didn’t shorten their routes further. Duos in which one bird was replaced after every 12 flights managed to further reduce the length of the route by 1.2 kilometers (nearly three-quarters of a mile).

“Apparently,” Biro says, “variation introduced by naive birds also allows experienced ones to do better.” The addition of a new individual also raised the amount of time duos spent on exploration, the team found. “So the naive bird also influences the more experienced animal’s behavior,” says Biro, “and they end up learning better routes because of it.” 

Biro and colleagues at Kyoto University in Japan also found an influence of inexperienced individuals on innovation when studying wild chimpanzees. Younger chimps, they observed, were more likely to try cracking species of nuts they hadn’t encountered before than older ones were. And in a 2017 report coauthored by Whiten, one chimpanzee figured out how to take the stopper off a piece of piping, then another one discovered how to drink otherwise inaccessible juice through it — and, ultimately, the behaviors were combined. “It took a while before one of them put the two things together,” Whiten says, “but eventually, they did.”

Cultural conservation

Studies like this reveal that some nonhuman animals are doing more than individually learning behaviors from others; rather, they may find better solutions together than they would on their own. In humans, thanks to a unique combination of exceptional social tolerance and collaboration skills, faithful cultural transmission, and almost laughably large brains, this process really took off, creating an extraordinary, self-reinforcing capacity for culture.

That has allowed us to do incredible things, but it has also made us vulnerable. Stripped of our cultural wealth, we would be entirely unable to survive in the wilderness, as many stranded explorers have experienced firsthand. Our cultural dominance also means that we have had a huge impact across the planet, making life difficult for all its inhabitants.

Does the cultural learning scientists are discovering in other animals make it easier for them to adapt to all this drastic change? Or does it render them more vulnerable, since culture may more rapidly be lost from dwindling populations?

It depends, says Aplin. Species such as tits that are quick to learn and to pick up what others have learned are likely to do well. “Their populations have remained robust to human disturbance,” she says. So might the sulfur-crested cockatoos she has been studying in Australian suburbs. Some of these birds have figured out how to open trash cans, a behavior that is now spreading across the population.

But species that depend on ancient knowledge passed down over generations may be at risk when populations decline, or when key individuals are killed. 

Think of elephant matriarchs who may be the only ones to remember where to find water during unusual droughts, or birds and whales that perform long-distance migrations. Some of these species have been hunted to near extinction, causing severe losses of diversity, cultural as well as genetic. In chimpanzees, a recent study revealed that human influence has caused a decline in cultural diversity across Africa. Thirty-one well-studied behaviors, from termite-fishing to the use of self-made leaf sponges to soak up water to drink, were 88 percent less likely to occur in areas classified as experiencing high impact from people.

Yet when given the chance, the space and the time, cultural animals often do have the ability to recover. A 2018 study showed how recovering bighorn sheep populations were relearning migration routes. Conservation workers have helped migratory whooping cranes raised in captivity to learn their species’ migration routes by having small planes show them the way. And when endangered golden lion tamarins were provisioned long enough to allow the adults to survive, their offspring were found to socially learn how to get by on their own in the wild. Clearly, conservation needs cultural awareness as well.