Did cooking make us human? New evidence from Kenya suggests early hominins were roasting meat over fires 1.5 million years ago. The discovery pushes back evidence of fire use by hundreds of thousands of years, and lends weight to the idea that cooked food helped trigger the evolution of big-brained humans.
鈥淚t鈥檚 very exciting,鈥� says Sarah Hlubik at Rutgers University in New Jersey. 鈥淭his is the oldest site to date with evidence of human ancestors using fire.鈥�
Hlubik and her colleagues found the evidence at a site in Kenya鈥檚 Koobi Fora region, which has a rich archaeological record. Parts of the site were first excavated in the 1970s and at the time researchers noticed unusual patches of reddened dirt. They were argued to indicate where ancient controlled fires had thermally altered the ground beneath.
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Excavations resumed in 2010, and since then Hlubik鈥檚 team has found evidence to bolster the idea that ancient hominins controlled and used fires on the site. The researchers collected thousands of fragments of stone tool and pieces of animal bone 鈥� some of which are burned 鈥� from across the site. Some patches of reddened dirt are surrounded by relatively dense clusters of stone artefacts and burned bone, as might be expected if hominins were sitting around a fire to eat .
Perhaps most significant is that a handful of the stone tool fragments have a distinct curved appearance, making them look a little like enlarged toenail clippings. In a second paper, the researchers found that this unusual curving occurs only when a stone tool is being made near a fire. Hlubik says that chipping away at a pebble to turn it into a tool seems to introduce physical stress lines in the fragments that ping off. If those fragments happen to fall into a hot fire, they then .
Stone age barbecue
The team says that that their findings do not prove hominins were using and controlling fire 1.5 million years ago, but they say the evidence they have collected does support such an idea.
Clear signs of controlled fire appear in the archaeological record only about 400,000 years ago, but Wil Roebroeks at Leiden University says we shouldn鈥檛 be surprised if the practice began much earlier. 鈥淚t would be na茂ve to think that we already have identified the earliest traces of fire use by hominins,鈥� he says. However, Roebroeks agrees with Hlubik鈥檚 team that the new evidence is suggestive rather than definitive.
The bigger question, says Hlubik, is how often hominins used fire to cook food 1.5 million years ago. Some researchers argue cooking became such a common practice between 1.5 and 2 million years ago that it shifted the course of hominin evolution. Cooked food is easier to digest, so hominins could 鈥渁fford鈥� to simplify their digestive tract and potentially divert energy to brain growth instead. Homo erectus, arguably the first hominin with a larger brain, .
But under that scenario we should find evidence of fire use at many ancient sites across the landscape. 鈥淭hat鈥檚 what we鈥檙e working on now,鈥� says Hlubik. The Koobi Fora region covers thousands of square kilometres and contains many sites of hominin occupation dating back 1.5 million years or more. Hlubik and her colleagues hope that they can find more evidence of possible fire use in some of these other sites. 鈥淥ne site is not enough to say that fire is what changed human evolution,鈥� she says.
Journal reference:听Journal of Human Evolution,听
Journal reference:听Journal of Archaeological Science,听
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