Chimpanzees have learned to cook

Researchers who worked with chimpanzees at the Jane Goodall sanctuary in the Congo concluded that everything needed for cooking, apart from the control of fire, was already created at an early stage of the development of the human race

Nowadays, cooking dinner requires no more thought than turning on the stove or oven, but for ancient humans, the notion that simply by adding heat or direct fire could make food tastier and easier to digest required cognitive insight. Until now, it was believed that such an insight exists only in humans. However, new evidence now emerges that when it comes to cooking, humans are not the only ones around the table.

A new study by Prof. Felix Vermken and Alexandra Rosti, as a postdoctoral fellow in the Department of Psychology at Yale University, who participated in the study at Harvard, suggests that humans share cognitive ability with chimpanzees. This includes a preference for cooked food, the ability to understand the transformation of raw food into cooked food and even the ability to store and transport food over distances for the purpose of cooking it.

The researchers' conclusion is that these abilities appeared at an early stage of human evolution and, except for controlling the fire, the chimpanzees are able to perform all the cognitive tasks involved in the cooking process. The research was published in an article on June 3 in the journal Proceedings of the Royal Society B. of the British Royal Society.

"Researchers so far have focused on the ability to start a fire, but even if you have a burning torch, more insights are needed before you can use it for cooking," says Rosati. It goes without saying that chimpanzees cannot control fire, but we tried to hypothesize about some of the other aspects of cooking such as the environmental understanding that if you put raw food on a fire, cooked food is created. Or as they discovered in the research, the ability to plan.

What is interesting about cooking is that it is an action that we all do, but it requires a number of abilities that, even without the connection to cooking, are considered unique to humans and this is what we wanted to test in chimpanzees."

To answer these questions, in the summer of 2011, the two traveled to the Chimupanga chimpanzee sanctuary at the Jane Goodall Institute in the Republic of Congo, where they performed a series of experiments on chimpanzees born in the wild to test whether they have the ability to make the mental leap required for cooking.

Their first experiments were dedicated to repeating previous studies - proving that the chimpanzees prefer sweet potatoes cooked in a hot pan without butter or oil, over uncooked sweet potatoes. They were willing to pay for it in time, meaning waiting long minutes to get their favorite cooked food.

Additional tests were designed to gauge whether the chimpanzees really understood the change from raw to cooked food, and if they would try to "cook" items spontaneously.

To investigate these questions, researchers presented the chimpanzees with two devices - a "cooking device" that turned proper sweet potato slices into cooked slices and a control device that left it unchanged.

During the experiment, the chimpanzees saw suitable sweet potatoes going into both devices but had to choose one device before seeing its contents (which could also be switched). Warnken and Rosati explained that almost all the chimpanzees chose the cooking device, which shows a quick understanding of how the change is made. It was the last experiment, however, that revealed the chimpanzees' ability to cook.

"We spent one season experimenting and thinking about what interesting things we discovered, but then we wondered if they would be able to wait for the prize and actively choose to put the sweet potato in the cooking device," Warnecht said. "It's really hard because usually when chimpanzees get food they eat it.

"I thought there was no way they would do that," Rosatti added. "The studies show that animals have problems with self-control in holding food, however, since we had to leave the shelter after a few days, we decided to test the hypothesis. To their surprise, she said, some of the chimps, given a slice of uncooked sweet potato, consciously chose to cook it by putting it in the "cooking device" and receiving a piece of cooked food in return.

The first time when one of the chimps did this I was surprised, because I did not expect it. I thought maybe it was one chimpanzee going crazy, but in the end about half of them did it," said Rosati.

With the surprising result, the two left Congo with a series of additional questions that will have to wait until their return next summer. Among these new questions was the question of whether the apparent understanding of the cooking process by the chimpanzees would be extended to other foods as well. Just like the chimpanzees used the "cooking device" to turn a raw sweet potato into a cooked one. The experiments showed that they did the same thing with carrots.

"The surprising thing here is that they had never seen a carrot inserted into these devices," Rosati explained, "but they were still able to generalize this process."
Another test checked whether you would try to cook anything. When the chimpanzees were given a piece of uncooked potato and a small piece of wood, they put only the potato into the cooking device, suggesting that they understood that only edible items can be cooked.

"It shows that they just don't see it as a barter situation," Rosati said. "They are not interested in putting anything random in the cooking device. They might be expected to put both in the vessel because they would get double the return, but they don't really care about the piece of wood."

In the last two experiments, the two focused on one of the most pressing questions in the field of animal intelligence - whether animals are able to plan for the future.

Although few studies have shown that chimpanzees are able to keep utensils for later use, "those studies looked at very different utensils than cooking utensils," Rosati said. ". A tool can be valuable because you can use it in the future, but you can't eat it now. When it comes to cooking there is something else - the food - that has intrinsic value."

Despite this value, the chimpanzees were willing to bring food from distant places to cook it. When given uncooked potatoes on one side of an enclosure, some of the chimps showed a willingness to carry them four meters to the cooking device on the other side.

"In some cases, they actually carried it in their mouths, and you could see that sometimes they would eat it, almost by accident," Rosati said. "It was a difficult problem, but they managed it in half of the cases.

To test whether the chimpanzees were able to save food for later cooking, in the experiments the chimps were given food but Warnken only appeared with the cooking device three minutes later.
"In the beginning it was very difficult for them" said Rosati. "But later on, they realized that it was going to come back, and so they realized that if they could keep the food for three minutes, they could turn it into cooked food. In the control experiment, they were given the same amount of food, but Warnken never appeared. The hypothesis was that they wouldn't be able to cook the food, they just ate it alive."
To their surprise, the two said, several of the chimps were able to perform the task, and two of them even saved almost every bit of raw food they received to cook later.

Although the study supports the hypothesis that cooking behavior appeared early in human history, Warkenten and Rosati say it may also prompt a rethinking of when humans first mastered fire.

"We cannot date the beginning of fire control through cognitive studies, but we can date the appearance of the other skills required for cooking," says Rosati. "The kind of evidence from the field of comparative physiology can tell us a lot about your evolutionary history.
I believe that the research supports the idea that cooking appeared early in human evolution because all the cognitive components were already there and all that was required was to control fire."

Despite the assumption that humans controlled fire for a long time before they started using it for cooking, the two show that cooking could have developed earlier than the control of fire.
Why would early humans be motivated to control fire? Rosatti asked? "I think cooking could be the reason. We know that when chimps in the wild spot a natural fire they go out to look for and eat cooked food left behind by the fire. The evidence from our cognitive studies indicates that, even before fire was mastered, early hominins understood that there was an advantage to cooking food over fire even if it was ignited accidentally and naturally.

For information on the Harvard University website