麻豆传媒

AT THIS time of year, as the temperatures drop, I find myself craving pies. I don鈥檛 know what unrecognised geniuses invented pastry and then had the idea to put a casserole inside it, but I owe them an unpayable debt. So let鈥檚 talk about the invention of cooking. How long have humans been deliberately exposing their food to heat to make it better?

You might remember a recent story reporting evidence that hominins were cooking carp fish in an earthen oven around 780,000 years ago in what is now Israel. Previously, the oldest unambiguous of cooking was from 170,000 years ago in South Africa.

The baked carp predates our species, Homo sapiens, by hundreds of thousands of years, so the chefs must have been Neanderthals or other extinct hominins. This is supported by , which described pulses that had been pounded and charred at caves in Greece and the Kurdistan region of Iraq. These sites are more recent, within the past 100,000 years, but Neanderthals are still the most plausible candidates for the cooks.

So we now know for certain that cooking isn鈥檛 unique to our species and that it was going on 750,000 years ago. What鈥檚 more, ovens are a fairly advanced form of cooking, compared with holding your food over a fire. To me, that鈥檚 a hint that cooking goes back even further.

For over 20 years, Harvard biologist Richard Wrangham has been promoting the hypothesis that hominins started cooking around 2 million years ago. That鈥檚 not long after our genus, Homo, evolved. Crucially, it is when brains evolved to be much bigger. Wrangham argues that cooked food, which is more nutritious and easier to chew, enabled the evolution of large brains.

When he first suggested it, this was a big swing because hard evidence of cooking was confined to relatively recent periods. However, absence of evidence isn鈥檛 necessarily evidence of absence. The most obvious traces of cooking are organic remains, which tend to decay 鈥� unlike resilient things like stone tools.

And as the years have passed, the evidence of cooking has been pushed back. Traces of ash and burned bone from a South African cave hint at cooking 1 million years ago, while a site in Kenya has evidence of hominins roasting meat on fires 1.5 million years ago.

The evidence for cooking sits alongside the growing evidence for controlled use of fire by extinct hominins. The tricky thing about the archaeological record of fire is that fires happen all the time anyway. Researchers must discern those started and controlled by humans from ordinary forest fires. In 2011, a systematic review found that controlled fire use could be traced back 400,000 years. That鈥檚 before the origin of our species, so Neanderthals (and possibly other hominins) could control fire.

In June, I was delighted to read about evidence of controlled fires 1 million years ago, in what is now Israel. Key here was the method. The team studied flints that showed no visible sign of having been heated. Examination of their response to UV light showed their crystal structure had been altered by heating to around 400掳C. This form of evidence could be more widely preserved and has the potential to show that Homo had control of fire 2 million years ago.

I should also mention the recent report that Homo naledi, ancient humans that lived in what is now South Africa, may have used fire to cook and to navigate in dark caves. The evidence for this comes from the Rising Star caves where the species鈥� bones were found. Deep in the caves, there are 鈥渉uge lumps of charcoal, thousands of burned bones, giant hearths and baked clay鈥�, according to Lee Berger at the University of the Witwatersrand in South Africa. That鈥檚 dramatic, but it comes with a colossal caveat: the team hasn鈥檛 dated this stuff yet, so it might be nothing to do with H. naledi.

H. naledi lived relatively recently, between 230,000 and 330,00 years ago, so their putative fire use wouldn鈥檛 extend the period in which hominins have controlled fire and cooked. However, H. naledi had small brains for such a recent hominin, so if they could do it, maybe earlier hominins were capable of it too.

We can get some clues about the earliest hominins鈥� relationship with fire by looking at modern ape behaviour. A published in April showed that savannah-dwelling chimpanzees often prefer to travel in regions that have recently been burned, and that they find more food in those places. It鈥檚 not hard to imagine hominins shifting from this passive use of fire to something more active. But when they did so remains wildly uncertain.

Taken together, all these studies have swayed my opinion about the cooking hypothesis. I鈥檓 still not convinced Wrangham is right, but my internal needle of scepticism has shifted. And now I want a pie.

Michael Marshall is a science writer based in Devon, UK. He writes 麻豆传媒鈥檚 monthly email newsletter Our Human Story, about human evolution. His book The Genesis Quest is about the origin of life on Earth and is now available in paperback.