Chimp Study May Give Insight Into the Evolution of Human Complexity

Apes that share and care are capable of achieving superior technological prowess when fishing for termites, science proves. Is this the origin of our cumulative culture?

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Ruth Schuster
Ruth Schuster

A study of wild apes sharing tools to catch termites could bring insight into the origin of cultural complexity in humans, suggest the humans behind the new study.

The motivating question behind the research is how cumulative culture develops. Going by the mounting complexity of stone tool culture in humans over hundreds of thousands of years, cumulative technology involving a learning process seems to go back to the dimmest reaches of human evolution.

Now, a team has had a stab at gaining insight on the origins of social learning by looking at wild chimpanzees who share termite-fishing gear, Stephanie Musgrave of the University of Miami, Crickette Sanz and colleagues suggest in PNAS

Our cousin the chimp, from whom our ancestors parted ways six or seven million years ago, is a famed tool user. Wild chimps have been known to use rocks as remotely applied accoutrements of aggression – meaning they can and will throw rocks at one another. They have recently been observed throwing rocks at specific trees for no obvious reason, which some scientists suspect may be a primitive ritual. One bonobo unexpectedly fashioned a spear to try to stab a scientist, but the irritated ape was captive, unable to escape her bane. And wild chimps fish for termites and manipulate the source material: they’re actually making tools, as opposed to picking up some blobject and using it as is.

So, seeking potential insight into early human propensities, anthropologists examined termite-fishing techniques and tool-sharing in two wide-separated populations of wild chimpanzees.

For what it’s worth, most people think termites are a sort of white, sun-fearing ant. Actually, they evolved from cockroaches. Now you know.

A chimpanzee using a stick to retrieve food from a hole in one of two artificial termite mounds at Sydney's Taronga Zoo.
A chimpanzee using a stick to retrieve food from a hole in one of two artificial termite mounds at Sydney's Taronga Zoo.Credit: AFP

Back to the chimps. One group living in Gombe, Tanzania, used only one type of tool – a fishing probe that could be made of twigs, vine, bark or grass – and resisted sharing, usually rejecting requests from other chimps, including their own kids.

A second group living in the Goualougo basin in the Republic of Congo sequentially used multiple, different types of tools, which the apes made from certain plant species. They modified the tools to improve efficiency and – as hypothesized by the scientists based on the complexity of the behavior – the Goualougo mother chimps proved to be three times more amenable to sharing the tools (mainly with the kids) upon request than their counterparts at Gombe, according to the new paper, published Tuesday in PNAS.

“We predicted that at Goualougo compared to Gombe requests or attempts to take tools would more often result in a change of possession,” the scientists write. And so it was.

In both groups, what sharing there was usually took place between mothers and offspring. In general, the chimps were much more likely to share tools with females and juveniles who asked for them, compared with males and infants. The kids, by the way, were perfectly capable of stealing tools; possibly they hadn’t yet learned how to ask nicely.

"A tool transfer is defined as a change in possession of a tool, which can occur in different ways. Mothers at Gombe do sometimes transfer tools, for example by allowing infants to take a fishing probe from their hands, or by picking up a fishing probe they (the mothers) have set down," Musgrave tells Haaretz. "Only at Goualougo, however, do chimpanzees exhibit active transfers, defined as an individual moving to actively facilitate a transfer after another individual requests the too"

Jane Goodall discovers chimps fishing for termitesCredit: The Jane Goodall Institute, YouTube
A juvenile chimpanzee termite-fishing.
A juvenile chimpanzee termite-fishing.Credit: Image courtesy of Christopher Wa

For example, in an active transfer, a mother chimpanzee might extend her arm to give it to a child or divide a tool in half lengthwise to produce two usable tools and then provide half to offspring, she says.

Males would sometimes share tools with young chimps but in general, the sharers were female, Musgrave says.

Plausibly, the willingness to share helped the Goualougo chimps develop and sustain relatively complex tool manufacture and use, the team suggests. Thus, they could be a model for early human behavior.

Monkey see, monkey do

In humans, cumulative culture is hypothesized to have begun with imitation and teaching – forms of social learning that enabled the accurate replication of complex behaviors.

Termites eating the wood of a house.
GRUBS UP: Termites eating the wood of a house.Credit: plew koonyosying / Shutterstock

Making stone tools by chipping a target rock using another rock goes back at least 3.3 million years. That is 3 million years before anatomically modern humans began to evolve.

The earliest stone tools were crude, large beasts that could weigh several pounds. By the time of the Neanderthal, stone tool technology had become quite a technological art. Some researchers infer that not only social learning but language may go back farther than we imagine, to precursors of modern humankind, based on the sheer complexity of stone-tool manufacturing processes developing over hundreds of thousands of years.

Chimps, crows and some other beings capable of complex tool-related behaviors don’t have schooling, but do have social learning – mainly, novices learning by themselves from other members of the species. It’s more monkey see, monkey do.

But the more prosocial the behavioral patterns, the more likely complexity is to emerge, according to the theory.

“Prosocial” refers to behaviors performed for someone else’s benefit: think of it as altruism-lite, with low cost. Prosocial fishing-rod transfers between apes count as teaching, the researchers argue: The tool-giver is forgoing potential food in favor of the tool-taker, and the sharing plausibly facilitates the novice’s learning process.

And communication – asking for the tool by whimpering or holding out a hand or other, as opposed to hanging around scratching fleabites until a tool is abandoned – is key.

At Gombe, requests were more likely to be met with resistance than at Goualougo, and the observed fishing behavior was commensurately simpler.

It also bears adding that tool acquisition skills at Goualougo lasted into subadulthood and the kids only learned how to make tools after they had learned to use them (to fish for termites adeptly).

Monkey say, monkey do

Wild chimpanzees live in permanent groups with multiple males and females, within which they tend to form fluid cliques. But in any case, they are characterized by strong social interaction and bonds. Maternal dependence in chimpanzees lasts for years. Baby chimps only start eating solid food at about 6 months and cling to or stay by the mother until the age of 3.5 years. They continue to nurse until age 4 or 5, and like humans only reach sexual maturity in their early teens.

The famous primatologist Jane Goodall discovered that orphaned baby chimps are often taken care of by others in the group, including in one case an older brother. That is charming.

Whoever the chimp kids stay with, it’s for years, and they have ample opportunity to learn – “education by master-apprenticeship,” as Tetsuro Matsuzawa called it.

What’s more, who knows: maybe the chimps really do talk. Captive ones can certainly be taught some sign language and researchers think they have managed to interpret no fewer than 66 gestures – sign language – in wild apes.

The current study observed that chimpanzee mothers at Goualougo, where technologies became complex, were three times more likely to share tools with the kids than mothers at Gombe, where tool-use was simpler.

The upshot seems to be that the cooperative chimps had developed and improved variegated methods of achieving their aim, feasting on plump juicy cockroach cousins, while the insular chimps had one basic method: "Chimpanzees at Goualougo, but not at Gombe, also intentionally modify herb probes to fashion the end into a brush tip. This modification makes the fishing probe ten times more efficient at capturing termites," Musgrave tells Haaretz.

And that could cast light on how technology transfer emerged in early archaic humans, ultimately resulting in the conveniences of modern society. You can’t teach young ’uns to manufacture a telephone or, at the other end of the spectrum, an F-15, by mime.