Heaps of fish teeth found at a waterlogged prehistoric site in today’s northern Israel have revealed an important new piece in the puzzle of human evolution. Hominins living at Gesher Benot Ya’akov 780,000 years ago were apparently capable of controlling fire to cook their meals, a skill once thought to be the sole province of modern humans who evolved hundreds of thousands of years later.

Evidence for the earliest meal cooked by hominins was published [November 14] in Nature Ecology and Evolution by a team of Israeli and international researchers.

What happened to all the bones? The most logical explanation was that the fish were cooked, because that process softens the bones (the same reason why gelatin is often made from fish bones), which in turn means any leftover bones would have decomposed quickly, leaving only the teeth for archaeologists to find nearly a million years later.

To test this hypothesis, [Dr. Irit] Zohar and colleagues analyzed the teeth using X-ray diffraction to look at the nanocrystals that make up the enamel. These crystalline structures expand when exposed to heat, explains Dr. Jens Najorka, X-ray lab manager at the Natural History Museum in London. And indeed, the crystals in the enamel on the fish teeth from Gesher showed a small size increase consistent with the application of low-to-moderate heat, under 500 degrees Celsius, Najorka says.

The low temperature is important, because it is indicative of cooking, while higher heat would have simply meant the remains were burnt by being thrown into the fire, as fuel or as a form of garbage disposal, Zohar says.

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