Humans began cooking 1.9mn years ago: Scientists

Researchers at Harvard University who studied tooth sizes and the feeding behaviour of extinct hominids, monkeys, apes and modern humans concluded that cooking was commonplace among Homo erectus, our flat-faced and thick-browed ancestors which lived 1.9 million years ago.

"We see a dramatic shift in the tooth size of Homo erectus, which means it was likely responding to a history already of eating cooked and processed food," said Chris Organ, an evolutionary biologist at Harvard.

"If you're cooking your food you have many more hours of your day free, and you can spend those hours doing other things, since you don't have to eat as much to get your daily requirements," Organ was quoted as saying by LiveScience.

Processed food is much easier to chew and digest and since chewing breaks up the food it means more surface area is available from which the gut can absorb nutrients, Organ said. The result means more available calories per serving and less gut time needed to digest those calories.

The research, published in the journal Proceedings of the National Academy of Sciences, found that chimpanzees spent 10 times longer chewing and eating than humans do, 48 per cent versus 4.7 per cent of their days.

It also found that Homo erectus, which emerged in Africa around 1.9 million years ago, spent 6.1 per cent of its time eating, while the Neanderthals spent 7 per cent of their time feeding. Statistical analyses placed these chew times within the range of time spent chewing for humans.

Looking back over two million years to a more distant relative, the researchers found that Homo habilis spent about 7.2 per cent of its time eating and Homo rudolfensis 9.5 per cent.

While these numbers are much smaller than the modern chimpanzee eating times, they fall on the border of the modern human spectrum, so the researchers couldn't definitively say that their changes in molar size were due to different feeding behaviours.

"The time they spent eating was on the high range of what we see in human cultures. We are a little less sure about those two species," Organ said.

"We stuck our flag in the sand with Homo erectus, because that's when we really start to see modern human-like feeding times, but it very well could have evolved earlier than that."

This extra time and calories likely had a large impact on the evolution of modern humans, and even the evolution of language and social lives, since you can't eat with your mouth full, and processing food can be a social activity, the researchers said.

This cooking and processing would have included roasting over a fire and mashing with stones. Their diet would have included vegetables, tubers and various kinds of meat.

The only snag is that the researchers didn't find much evidence of fire-based cooking from this far in our past. The oldest evidence of fire use by hominids is around one million years ago.

"There isn't a lot of good evidence for fire. That's kind of controversial," Organ said. "That's one of the holes in this cooking hypothesis. If those species right then were cooking you should find evidence for hearths and fire pits."