If you found yourself among a group of chimpanzees in the wild, you could not expect to be served a home-cooked meal.

If it's cold, tough. You will not be warmed by a carefully lit fire, unless of course you lit one yourself.

But while chimps may lack these skills, there is new evidence to suggest they do have the mental abilities to understand the benefits of cooked versus raw food. With some training they are even able to "cook" raw food.

The findings could help explain the importance of cooked food in our own evolution. 

Think about it for a moment and you will realise several different thought processes go into cooking. For us they are almost automatic.

We know that waiting and preparing something nice is better than stuffing ourselves with a bunch of raw vegetables and meat. We also have to gather the necessary ingredients and then assemble them.

When agriculture began to flourish over 10,000 years ago, our farmer ancestors had to plan ahead even more to grow crops to harvest at a later date. Planning, working together and anticipating the rewards all come into play. 

It makes sense that we prefer cooked food. "The hypothesis is that cooking can allow us to make things more digestible and extract energy more efficiently," says Felix Warneken of Harvard University in the US.

We certainly need as much energy as we can get, as our brains are very costly. They use up about 20% of all our body's energy, so fuelling them has been crucial to our success as a species.

After we discovered how to use fire, cooking is one of the key things that could have helped make us who we are today.

One theory proposes that it began as early as two million years ago, around the time our hominin ancestors began to evolve bigger brains. The primatologist Richard Wrangham, also at Harvard University, suggested this over a decade ago.

However, it has been difficult to back up as there is no evidence of fire use older than one million years.

Our teeth are kind of pathetic

So it's not clear when all these necessary skills came together and allowed us to cook. This is where comparative work on our closest relatives, chimpanzees, becomes useful.

It is already well-established that many animals, given the choice, prefer food that is cooked. Why wouldn't they? It is softer, easier to digest and can be tastier.  

But unlike us, they don't depend on it. Many animals like chimpanzees have strong teeth, jaws and a digestive tract well suited to the raw food they consume.

Humans are a different story. "Our teeth are kind of pathetic," says Warneken, and we have smaller digestive tracts than chimpanzees.

As a result, we can't readily eat raw meat, especially if it is full of tendons and bones.

Nine new experiments on the evolution of cooking have now been published in one paper in the Proceedings of the Royal Society B. They used up to 29 chimpanzee subjects from a semi-free-ranging sanctuary in the Republic of Congo.

First, the researchers confirmed that chimpanzees prefer cooked food. They then went further to show that they can understand the difference between raw and cooked food.

In one experiment, the chimpanzees chose to place raw food into a small cooking device so that it would transform from raw into cooked. They would not do the same for, say, a stick.

This blew our mind because usually when chimpanzees have food they hold onto it

"That was preliminary evidence that chimps may understand the transformation process, that something currently raw is later cooked," says Warneken, who co-led the study with Alexandra Rosati, also soon to be at Harvard University.

The team also tested the apes' patience. They delayed their own gratification in order to wait for the tastier cooked food.

And could they cook themselves? Well, almost, but only after the right prompts. In this case it came in the form of a clearly demonstrated small cooking device. The chimps would place raw potatoes into it so they could eat them cooked later. 

"This blew our mind because usually when chimpanzees have food they hold onto it and maybe even eat it right away," says Warneken.

"That these chimps would be willing to give up the food so that it could be cooked was quite amazing. It shows not just their cognitive understanding but also the inhibitory control that they have."

In a further test, the chimpanzees transported their food several metres in order to have it cooked, thereby demonstrating even more planning and anticipation.

They also learnt to do so very quickly. So Warneken suggests that our early ancestors would have started using fire to cook food as soon as they discovered it.

If chimps have such a high level of cognitive understanding of cooked food, even delaying immediate gratification to have it, it suggests our early ancestors did too.

For instance, the ape-like Australopithecus - which famously included the female known as "Lucy" - lived 2-4 million years ago. They were remarkably similar to chimpanzees, with only slightly bigger brain cases.

Wrangham proposes that australopithecines "could indeed have found a way to use fire to cook food", using their slightly superior brainpower.

"I hope that this study continues to encourage archaeologists to find new ways to test the prediction that I favour, which is that hominins began using fire around two million years ago or earlier, well before the current earliest strong evidence at one million years ago," he says.

Eating cooked food could have been instrumental to our own group, Homo,evolving bigger brains, Wrangham argues. "Cooking is strongly expected to lead to higher rates of energy flow to the brain," he says.

"Furthermore, Homo erectus colonized not only Africa but also all of Eurasia, which I believe was very much due to their use of cooked food."

Nevertheless, it remains the case that chimpanzees are extremely competitive when it comes to food. In the wild, it's much safer to consume it straight away, otherwise a dominant member might simply steal it. Also, chimps don't have fire.

"Even though chimpanzees are close [cognitively], they are not fully there," says Wrangham. "The first fire user needed to be a little more intelligent than chimpanzees."

In other words, our closest relatives have the brain power needed to cook food, but left to themselves they would never use it. For them, it's better to be a bit more selfish and impulsive when it comes to food.

"Even if you have the cognitive skills to cook food, if the mutual trust isn't there, these skills cannot be used in a meaningful way to become a critical component of human life," says Warneken.

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