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(Image: Alexandra Rosati)

Why try to gauge the ability of chimpanzees to grasp the concept of cooking?
Cooking food spurred a fundamental change in the human species. Cooking makes many foods more digestible and allows us to extract more energy 鈥� things we need to sustain our large brains. But we don鈥檛 know when or how cooking evolved.

By looking at our closest living relatives, chimpanzees, we have an opportunity to make comparisons with our closest evolutionary ancestors and see whether they might have had the core cognitive skills to cook food. It鈥檚 almost like we can step into a time machine that can help us better understand our evolutionary past.

Do chimpanzees have the abilities required for cooking?
Cooking requires a lot more than just access to a fire. It takes a lot of patience. You have to resist the urge to eat the raw food, you have to understand the transformation process and you have to hold on to the food and transport it so it can be cooked in the future.

It is a more complex skill set than you might think 鈥� and requires a good bit of inhibiting impulses. So we tested all of those cognitive skills across nine experiments and found that , although not a fully sufficient set.

And that tells us that those abilities were probably part of the repertoire of the last common ancestors of humans and chimpanzees and so evolved fairly early in evolutionary time.

How did you give chimps access to cooking? Surely you didn鈥檛 let them play with stoves?
Obviously, we couldn鈥檛 use fire to cook because it would be dangerous. So to test the chimpanzees鈥� understanding of the transformation, we created a novel cooking device. Really, it was just a magician鈥檚 box with a simple false bottom where we would put the cooked food.

The chimpanzee would place a slice of raw potato into the device, shake it, and then the cooked slice would appear. So it seemed as if the raw food turned into cooked food. But it worked. Even after a single session, the animals reliably wanted the cooking device so they could 鈥渃ook鈥� their potato.

You discovered that the chimpanzees could transport raw food for cooking. Can you tell me more about that?
In the wild, chimpanzees tend to forage 鈥� they just snack while they go. But cooking requires you to take the food back to somewhere to do the cooking. And it鈥檚 not that easy. Even we humans sometimes can鈥檛 resist the urge to nibble as we are cooking our own dinners. But many of the animals were able to do it. We saw one chimp try very admirably to carry the food 4 metres to the cooking device.

But unfortunately, he tried to carry it with his lips, so he kept 鈥渁ccidentally鈥� eating it. Another chimpanzee would run over to the cooking site very quickly, holding the piece of potato as far away from himself as possible, seemingly so he wouldn鈥檛 be tempted. It was challenging for them, but many of the chimps were still able to anticipate cooking in the future and therefore save food for that future use. It was remarkable.

Were you surprised by your findings?
I鈥檝e been working with chimpanzees for over 10 years 鈥� and they keep surprising me by how smart they are. It鈥檚 amazing how quickly they learn and make inferences.

It鈥檚 important to understand that we don鈥檛 train the chimpanzees in any of these studies. We simply show them a certain kind of problem and then watch how they solve it. And, as you observe them, it鈥檚 like you can actually see the light bulb go on. They really do offer us an amazing opportunity to better understand how some of our most complex behaviour may have evolved.