When Did We First Gather Around the Campfire?

Humans and ants are the respective masters of their environments. This is due to novel social behaviour, at least that’s the argument of late biologist E.O. Wilson in his bestselling book The Social Conquest of Earth. Unlike other animals, humans and ants live in highly complex societies where there’s what can be called “reproductive division of labour”. Some members of the species voluntarily forego their ability to reproduce in order to secure the well-being of the group at large.

Think of soldiers fighting a war. They’re young kids who give up their life for a nation consisting of millions of people they’ll never meet without having had a chance to get children of their own. Although some soldiers are conscripted, a substantial number put themselves in harm’s way voluntarily. They thereby risk that their genes are lost from the human gene pool. They go genetically extinct.

From an individual point of view, this behaviour doesn’t make any sense. But as a species-wide survival strategy, the gains are enormous. A single member of a group can give up his or her life to secure the survival of the rest of the group. The group can then grow stronger down the line. This kind of social behaviour is known as “eusociality”.

Wilson’s evidence for human eusociality was based on the use of campfire in human prehistory. The alliances formed and broken around the campfire, as well as the complex social coordination needed to hunt animals that are, on their own, much more dangerous than humans, was what drove the human movement towards (occassional) social altruism. Whilst the theory is intriguing, there’s one problem: the evidence for human fire-use is quite recent, only 200,000 years old.

This could explain our own species, Homo sapiens, of course, but older human species such as Homo neanderthalensis or Homo erectus would predate fireuse by a couple of hundred thousand to more than a million years, respectively. Yet there’s nothing to suggest substantial social differences between our own species and our closest ancestors.

Now, researchers from the Weizmann Institute of Science have recently uncovered human fire-use in the Middle East that’s 800,000 years old, effectively predating our own species by 600,000 years. We’re not the only humans to have used fire deliberately, it seems.

They did it by relying on AI instead of the human eye. Traditional studies have focused on acquiring physical evidence of fire-use, such as charcoal. But this evidence isn’t robust enough to survive eons, which explains why only five sites have been found using this method that predate 200,000 years. The deep machine learning method that the Weizmann researchers used relied instead on reading chemical compounds from materials, which allowed them to assess the temperatures that specific materials had seen. This way, they had evidence of stone tools heated to more than 600 degrees C. They also found evidence of heating in animal remains.

Using AI technology to read the chemical signatures of materials on a molecular level, the Weizmann researchers were able to prove delibare heating in ancient stone tools. The technique should be widely applicable to materials such as this palaeolithic flint axe, dating to between 400,000-50,000 years ago from England. Image: Eloise Markwick.

This would all point to deliberate fire use.

And fire is a big deal. With it, we’re able to cook our food. This kills potentially deadly microbes in meat and allows for a higher nutritional intake as digestion becomes easier. Most experts seem to agree that cooking food was an essential step in the evolution of the human brain.

So although Wilson didn’t have sound evidence for the deliberate use of fire a million years ago when he wrote his book, new research seems to support his theory. Perhaps other researchers adopting the techniques of the Weizmann scientists can help illuminate the first human use of fire even further. This will only help to shed light on why humans are one of the most successful species around.

Cover image: Ville Palmu.

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