Although scientists have found evidence of charred bones around human fires that burned as long as 1.5 million years ago, that evidence hasn’t been enough to prove that the humans were cooking. However, a study published today (November 14) in Nature Ecology & Evolution argues that humans were cooking fish at least as far back as 780,000 years ago. The authors’ discovery of apparently cooked fish teeth would be the earliest documentation of the food preparation method by hominins, the scientists write in the study.
The discovery is the culmination of nearly 16 years of work at a site called Gesher Benot Ya’aqov, reports the Agence France-Presse. A 780,000-year-old settlement located in Northern Israel, the site contained a motherlode of freshwater fish remains and evidence of hearths likely made by Homo erectus, the authors write in the study. In areas of the site that contained “phantom” hearths, or areas only identifiable as hearths because of their high concentration of flint artifacts, the researchers also report in the study a large quantity of teeth belonging to Jordan himri (Carasobarbus canis) and the Jordan barbel (Luciobarbus longiceps), large species of carp with high nutritional value. However, they found no other fish bones. According to New Scientist, this could be evidence of cooking: When fish are cooked at a low temperature, the bones can become soft and disintegrate, whereas the enamel-covered teeth remain.
Investigating this theory, the researchers used X-ray diffraction to determine the size of the crystals in the fish tooth enamel. They then took fresh teeth from black carp (Mylopharyngodon piceus) and exposed them to temperatures ranging from 212–1652°F. Comparing the crystals in the ancient teeth to the modern teeth, as well as to fossil fish teeth they knew hadn’t been exposed to heat, the researchers found that the Gesher Benot Ya’aqov fish teeth had a crystal structure indicative of having been exposed to temperatures of around 400–930°F. This range was too low for the teeth to have been thrown directly into the fire, and right around the range needed for well-cooked fish, the scientists report. They posit that the fish were likely cooked whole in some sort of earthen oven.
Prior to this study, the earliest accepted evidence of humans cooking only dated to about 170,000 years, the scientists write in the study. Although charred food remains had been found much further back in the record, these remains weren’t a smoking gun for cooking, Irit Zohar, a study author and archaeologist at Tel Aviv University, tells New Scientist. “Evidence of charred material doesn’t mean cooking, it just means the food was thrown into the fire,” she says.
The researchers found the same patterns of fish teeth in different sites throughout the settlement, which spanned many generations, implying that cooking fish was a continuous tradition for the hominins at the site. “The fact that the cooking of fish is evident over such a long and unbroken period of settlement at the site indicates a continuous tradition of cooking food,” study author and Humboldt University of Berlin archaeologist Naama Goren-Inbar states in a press release from Tel Aviv University. “It is even possible that cooking was not limited to fish, but also included various types of animals and plants.”