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 Monday in Nature Ecology and Evolution by a team of Israeli and international researchers.
It was already known that early humans at Gesher, as well as at even older sites in Africa, could use fire. But this is the first time that archaeologists have been able to prove that such distant ancestors of Homo sapiens could control combustion to cook food.
The discovery has implications for our understanding of how humans evolved and reveals that our so-called primitive predecessors were much more advanced than we thought, the researchers say. It also highlights the role of fishing versus the contribution of hunting in humanity’s development, they say.
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Gesher Benot Ya’akov (“Daughters of Jacob Bridge” in Hebrew) is located on the banks of the Jordan River. It was once a rich, marshy area on the shores of the Hula paleo-lake, and for some 100,000 years hominins would return there to hunt and feast on giant two-meter-long carps, elephants, as well as local fruits and plants.
Burnt flint tools previously found at Gesher had suggested that the locals knew how to use fire, but scorched artifacts or sediments are often not enough to tell us whether the fire was natural, accidental or purposely made and controlled, and whether it was used for warmth or cooking or garbage disposal.
This is also the problem at earlier prehistoric sites in Africa possibly associated with fire use, such as the 1.9-million-year-old burned sediments at Lake Turkana and the million-year-old ash of Wonderwerk Cave in South Africa.
But at Gesher, the excavators noticed something unusual, says Dr. Irit Zohar, an archaeologist and marine biologist at the Natural History Museum at Tel Aviv University and at Oranim Academic College. In the same layers with the burnt flints, some 40,000 fish remains were found, of which more than 95 percent were teeth, says Zohar, who is the lead author on the new study.
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, 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.
Previous research had shown that the burnt flints found at Gesher were not distributed randomly – as if they had been burned in a natural bush fire – but were located in dense concentrations, likely marking the spots where, over tens of thousands years, hominins purposely and repeatedly made hearths and lit their fires. The results of the latest study only reinforce the conclusion that the locals could control fire, says Naama Goren-Inbar, an emerita professor at the Hebrew University of Jerusalem and the archaeologist who has headed the dig at Gesher.
The relatively low temperatures at which the fish were cooked mean, by definition, that they must have been exposed to a controlled fire, she says. Had they been burnt by a natural source, like lightening, which produces much higher temperatures, the results of the analysis would have been completely different, or there might not even be any teeth left to study, she notes.
We can’t be sure of how hominins cooked the carp they caught on the shores of Lake Hula, but, given the relatively low temperatures involved, the researchers speculate the succulent fish may have been prepared in earth ovens built next to the fire, possibly after being wrapped in giant waterlily leaves that were easily available at the marshy site, Zohar says. (Carp don't have teeth as we think of teeth, but pharyngeal teeth in their upper throat.)
The first chefs
No human bones were found at Gesher, as in many other prehistoric sites, so we can only guess at which type of hominin was participating in this Lower Paleolithic version of MasterChef. However, the timing of the site as well as the type of stone tools found there point to a chief suspect, Homo erectus, or one of his regional variants, Goren-Inbar says.
Erectus was the first hominin to leave our ancestral African home, around 1.8 million years ago, and spread across Eurasia. He is also believed to be the first to have mastered the use of fire, given that those indications of burning at Turkana and Wonderwerk are also associated with erectus.
And now we know that this hominin not only used fire but could control it to cook his catches.
“Cooking is never assigned to such distant times,” Goren-Inbar says, noting that previously the earliest firm evidence of cooking went back only to around 170,000 years and was linked to sapiens.
“When you speak about modern humans, Neanderthals or archaic sapiens, you assume that their cognitive abilities were all there, but we have shown time and again that as early as Homo erectus or his associates hominin abilities were much more sophisticated than anyone thought,” Goren-Inbar says. “They already had a big bundle of cognitive abilities.”
The archaeologist suspects that erectus may have already had the ability to cook before leaving Africa, but this still needs to be conclusively proven, she says.
Researchers have long suspected that cooking had a key role in our evolution, as proposed for example in the 2009 book “Catching Fire: How Cooking Made us Human,” by anthropologist Richard Wrangham.
Fish for brains
Cooked food required less energy to chew and digest than raw fare, giving hominins more bang for their buck, that is, more net calories for what they ate, says Prof. Israel Hershkovitz, a physical anthropologist at Tel Aviv University. If less strength was needed to chew, evolution could select for smaller teeth, leaving more space in the skull for a bigger brain, while the high-energy diet could fuel our expanding mental capacity, Hershkovitz says.
Researchers disagree on how hominins balanced their diets between meat, fish and plants, and how food influenced our evolution. Some experts think it was a pretty equal mix. Others support the theory that mammals, especially large animals with high amounts of nutritious fat, were the preferred source of food for our ancestors. And yet others propose that the fatty acids in fish played a particularly key role in fueling our developing brains.
“There is a big debate between anthropologists on how important fish were to human evolution, to the point that some think the fatty acids jumpstarted our brain growth,” Hershkovitz says. “I don’t know whether this is an exaggeration and how much of a game changer it was, but it certainly had an important role.”
Whatever the evolutionary advantages, fish were also much better value for money (or effort), Zohar notes. They were available in the freshwater sources that humans needed to be close to anyway in order to survive. Giant carps like those found in Lake Hula could be easily caught with bare hands, were available all year-around and their fatty meat provided several tasty and nutritious meals for a large group, she says.
So while we are used to thinking of prehistoric humans intrepidly hunting large animals (often into extinction), fishing, when available, may have been the preferred option, as it certainly beats getting stomped on by an elephant while trying to take down the pachyderm with a flimsy spear.
“Fishing was very important,” Zohar contends. “We like to think of ‘man the hunter’ but fishing gave us more stability and economic value than hunting.”