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Did Human Ancestors Use Hot Springs Like Instant Pots?

Illustration of hominids poking wildebeest in hot water with a stick
Tom Björklund

We tend to think of the control of fire as the first advancement that led to our ancient ancestors to cook their food. But new research out of MIT shows that these early hominids might have been boiling their wildebeests in hot springs long before they were grilling them.

Surprise!

The researchers came to this conclusion after exploring the Olduvai Gorge in north Tanzania—a site where fossils of hominids who lived 1.8 million years ago have previously been found. Lead researcher Ainara Sistiaga had headed to the site to explore an unusual band of sediment comprised mostly of sand that stood in contrast to a darker clay layer below. She had hoped to use her analysis to find out what was happening environmentally at the time. She thought that maybe it was related to East Africa’s change from a wetter tree-rich environment to one that was dryer and grassier.

“Something was changing in the environment, so we wanted to understand what happened and how that impacted humans,” said Sistiaga.

When she got her samples back to the lab, she began to look for lipids that are produced by leaf waxes, which would indicate what kind of vegetation was thriving at the time.

“You can reconstruct something about the plants that were there by the carbon numbers and the isotopes, and that’s what our lab specializes in, and why Ainara was doing it in our lab,” said Roger Summons, the Schlumberger Professor of Geobiology in MIT’s Department of Earth, Atmospheric, and Planetary Sciences (EAPS). “But then she discovered other classes of compounds that were totally unexpected.”

A Link to the Past

What she found were lipids produced by bacteria that Summons himself had found about 20 years ago in Yellowstone National Park’s hot springs. These bacteria only thrive in extremely hot water, so the researchers concluded that their presence in the ancient sediment means that hot springs were present at the time. Combined with the fact that the Tanzania site has already yielded stone tools, fossils of Home erectus, and animal bones, the researchers conclude that it’s not a stretch to assume that a community living near-boiling water with access to tools and food would have used that water to cook.

“If there was a wildebeest that fell into the water and was cooked, why wouldn’t you eat it?” Sistiaga poses.

Unfortunately, there’s no guaranteed way to tell if food was indeed cooked this way, but the researchers believe their findings are the first to suggest the possibility.

“We can prove in other sites that maybe hot springs were present, but we would still lack evidence of how humans interacted with them,” said Sistiaga. “That’s a question of behavior, and understanding the behavior of extinct species almost two million years ago is very difficult. I hope we can find other evidence that supports at least the presence of this resource in other important sites for human evolution.”

The research has been published in the peer-reviewed journal PNAS.