Raw food cooked over fire is considered a uniquely human evolutionary trait requiring tremendous cognitive foresight. Doing so requires planning of what to cook, how to cook it and why it should be cooked in the first place, not to mention grasping the concept of using heat to transform food in the first place. Humans may have perfected the art of cooking, but new research out of Harvard University suggests our closest relatives would feel right at home at our dinner tables: Chimpanzees have the cognitive capacity to plan for, understand and even to prefer cooked foods over raw.
Alas, the poor buggers never did figure out how to make fire, which appears to be their only obstacle.
“Obviously, chimps can’t control fire, but we were trying to hypothesize about some of the other aspects of cooking, like the causal understanding that if you put this raw food on the fire it creates cooked food, or, at the extreme end of our study, the ability to plan. What’s particularly interesting about cooking is it’s something we all do, but it involves a number of capacities that, even without the context of cooking, are thought to be uniquely human. That’s why we wanted to study this in chimpanzees,” said co-author Alexandra Rosati, a postdoctoral fellow in the psychology department of Yale University who will join Harvard’s Department of Human Evolutionary Biology as an assistant professor this summer.
The importance of cooking in human evolution cannot be understated. At a basic level, cooked food is safer and less likely to harbor dangerous bacteria against which early peoples would have had no defense. Cooked food also travels well, allowing populations to plan in advance for expansion. More importantly, perhaps, cooking may be the reason humans were able to rise to dominate the planet: Cooking food effectively pre-digests it for us, meaning we needed smaller stomachs than similar apes and primates. A smaller stomach meant more resources could be allocated for larger brains, the reason we’re here today.
The study took place at the Jane Goodall Institute’s Tchimpounga Chimpanzee Sanctuary in the Republic of Congo, where tests were conducted with wild-born chimps. The first tests were simple – did chimps prefer sweet potatoes cooked in a dry pan, and were they willing to wait for one minute for the cooked food? The second test was more complicated: Chimps were given the option of one of two “cooking devices” – raw sweet potatoes were fed into each, but only one produced cooked slices. The chimps reliably chose the device that produced cooked food.
The researchers say the third and most complicated test was what really drove things home for them. Would the chimps, if given the raw ingredients, have the restraint to actually place them into the “cooking devices” rather than simply running off with the free food?
“I thought there was no way they were going to do this,” Rosati said. “There is quite a lot of research that says animals have problems with self-control when it comes to possessing food, but we were leaving the sanctuary in a few days so we decided to try it.”
Surprisingly, chimps began to choose to use the cooking device, and all told about half opted for it, suggesting that it wasn’t simply a matter of a few super-smart chimps making the leap. Another test, in which chimps were given both a raw potato and a block of wood to place in the cooking device, suggested that the chimps truly understood that only edibles could be cooked.
“That shows they don’t simply view this as a trading situation,” Rosati said. “They’re not interested in putting any random thing in the cooking device. You might expect them to put both in because they’d get twice as much, but they really don’t care about the wood piece.”
Later testing continued to confirm chimpanzees’ understanding of cooking. They demonstrated the ability to transport food for the purposes of cooking, tested for by placing the sweet potato and the cooking device about 13 feet apart. They also (and most remarkably) showed that they could obtain food now for the purposes of cooking it later. The researchers would give the chimps the potatoes, and three minutes later they would return with the cooking device. It took some time, but once they realized that the device would return, several decided it was worth the wait.
It’s worth noting that this isn’t behavior learned over years or even generations, but over the course of a small study.
The researchers say the findings make it worth reconsidering our understanding of how and when people came to control fire and cook with it. Though it’s long been believed that we controlled fire before we thought to cook with it, the scientists believe that an innate understanding of the superiority of cooked food may have been a driving force.
“Why would early humans be motivated to control fire?” Rosati asked. “I think cooking might give you a reason. We know wild chimps will observe natural fire, and they even sometimes seek out and eat cooked food left behind by it. The evidence from our cognitive studies suggests that, even before controlling fire, early hominins understood its benefits and could reason about the outcomes of putting food on fire.”