Chez Chimp: Why Our Primate Cousins Don't Cook

Once upon a time, the list of behaviors that absolutely distinguished humans and non-human primates was clear and well defined. Tool use, language, organized group violence... some more debatable than others, but research on each of these has established that it no longer clearly defines a human leap forward.

Can we can add another activity to this list? That depends on how you interpret new research.

The New York Times headlined its coverage "Chimpanzees Would Cook if Given the Chance," writing that

chimps have the patience and foresight to resist eating raw food and to place it in a device meant to appear, at least to the chimps, to cook it.

The research article, published in Proceedings B of the Royal Society, explores the cognitive potential of chimpanzees. The researchers set up an ingenious experiment. Knowing from previous work that chimpanzees offered cooked tubers preferred them to raw ones, they examined whether chimpanzees would use a technology that appeared to transform the raw to the cooked.

In these experiments, chimpanzees who placed a sweet potato slice (or carrot) in a special bowl were offered a cooked slice already present in the same bowl, under a false bottom.

Basically this is a magic trick, adapted to simulate the effects of cooking.

I am not sure the researchers ruled out the possibility that the chimpanzees saw through the trick involved, using the false-bottom vessel as a mechanism of exchange—nasty raw food in, exchanged for yummy cooked food out.

The authors tried to test this by giving chimpanzees a wood chip, observing that they were less likely to put the inedible wood item into the "cooking" device. That does show they saw the device as specific for edibles—but doesn't entirely demonstrate an understanding of the process as "cooking."

The Times quotes the postdoctoral supervisor of one of the authors in a similar vein:

it was hard to know what chimps understood about the transition from raw to cooked food...similar questions could be asked about “most teenagers who are microwaving their pot pies."

Pause for massive outrage by any undergrads reading this. Not my example...but you get the point.

The authors of the study are more precise than the press coverage. They state that their research was designed to test if chimpanzees had a combination of skills they argue are required for cooking food:

motivation, patience, inhibitory control, causal understanding and planning.

The experiments convincingly show that at least some chimpanzees can restrain the impulse to eat food right away (inhibitory control), that they are motivated to obtain tastier forms of food if possible, that they understood that using the apparatus yielded the more desireable food, and (implied in all this) they could make a plan to trade in raw food for cooked.

I love this as illumination of the inherent capacities of chimpanzees. But why does research like this have anything to do with human evolution?

There are two ways to respond to that. The first is that there is a pretty heated debate in anthropology about the evolutionary benefits of cooking food and controlling fire. A few years ago, the British newspaper The Guardian summarized the issue well:

The advent of cooking was one of the most crucial episodes in the human story, allowing our ancestors to broaden their diet and extract more calories from their food. Because it softened food, it also spelled an end to the days of endless chewing.

As they went on to note, the main argument used for when cooking began has been the timing of apparent control of fire, on the order of 400,000 to 800,000 years ago.

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The research that The Guardian was commenting on used a different line of evidence: reductions in the size of molars, unrelated to reduction in general body size. Homo sapiens and Homo erectus shared a tendency toward smaller molars, dating the use of cooked food to about 1.9 million years ago.

The new study suggests that all the cognitive abilities needed to move to cooking food must already have existed in the common ancestor of chimpanzees and humans, consistent with the inferences based on study of molars.

The other response to the "what does this have to do with human evolution" is that it doesn't. Modern chimpanzees are not ancestors of humans; this new research tells us more about the cognitive capacities of our cousins, and isn't about us.

Take that, you solpsistic sapiens.

From this perspective, the concluding discussion of the new research by the authors, Felix Warneken and Alexandra Rosati, is most interesting for what it says about why chimpanzees, with their equally long evolutionary history and demonstrated preference for cooked tubers, did not develop their own culture of cooking.

It isn't that wild chimpanzees avoid fire or cooked foods; Warneken and Rosati write that

wild chimpanzees will calmly monitor the movements of natural fires, and even actively seek out roasted seeds from burnt habitats.

Instead, Warneken and Rosati conclude that human ancestors had motivation to cook that chimpanzees lack outside of laboratory conditions because of their dietary preferences:

Chimpanzees rarely consume tubers and roots in the wild, whereas hominin diets uniquely incorporate starchy tubers. Whereas chimpanzees preferred cooked tubers, cooking has little impact on their preferences for more typical chimpanzee foods such as fruits. The psychological barriers (such as inhibitory control) to cooking raw tubers are also probably reduced compared with fruits, as raw tubers are more difficult to digest and have low caloric value.

In other words: chimpanzees don't cook because they prefer foods that aren't improved by cooking. (In their opinion! Grilled figs having passed them by, apparently.)

So with all due respect to NPR, while "Chimps are no chumps," as long as they have access to their preferred foods, just giving them an oven won't make them cook. Chimpanzees are not the "frustrated chefs of the animal kingdom."

That's anthropomorphism. Chimpanzees, we now know, have a suite of cognitive capacities that also are necessary for the emergence of human cooking practices. And that is news—about chimpanzees.