It’s been suggested that cooking our food made us human. Toasting and roasting animal protein on a fire allowed us access to more nutrients and energy, providing us with the building blocks needed to fuel a big brain. However, a new study suggests we did not need to harness fire to unlock these much-needed nutrients. Instead, our ancient ancestors may have turned to natural hot springs to boil their meat. Hydrothermal-cooked wildebeest, anybody?
A recent archaeological discovery found evidence of hot springs near sites where ancient hominids settled some 1.8 million years ago – long before they learned to control fire – at Olduvai Gorge, a rift valley setting in northern Tanzania. Reporting their findings in the Proceedings of the National Academy of Sciences, archaeologists from the Massachusetts Institute of Technology (MIT) and the University of Alcalá in Spain argue that it’s no coincidence humans settled here.
Their findings suggest the area was once rich in hydrothermal vents that were capable of simmering the water at over 80°C (176°F). It also appears the vents were located very close to sites of early human settlements found featuring stone tools and animal bones. Given the unique timing of this early presence, it raises the intriguing possibility the hot springs could have been used by early hominins to cook food.
“If there was a wildebeest that fell into the water and was cooked, why wouldn’t you eat it?” lead author Ainara Sistiaga, a Marie Skłodowska-Curie fellow based at MIT and the University of Copenhagen, said in a statement.
The idea first came about in 2016 during an archaeological expedition in the Olduvai Gorge that saw researchers collecting sediments from a 3-kilometer-long layer of exposed rock deposited around 1.7 million years ago. Oddly, this sandy geologic layer was strikingly different from the dark clay layer just below, which was deposited 1.8 million years ago. This lines up with a big environmental change that occurred in East Africa at the time when this corner of the world shifted from a wet and lush land to dryer, grassier terrain.
They also discovered signs of lipids that are produced by specific groups of bacteria that the researchers discovered living in the hot springs of Yellowstone National Park. This strongly hints that hot springs were bubbling away at the time when hominids started to settle there.
“They won’t even grow unless the temperature is above 80°C (176°F),” explained Professor Roger Summons of MIT. “Some of the samples Ainara brought back from this sandy layer in Olduvai Gorge had these same assemblages of bacterial lipids that we think are unambiguously indicative of high-temperature water.”
If there were hydrothermal features there, it’s unknown how an extinct species might have interacted with them around 1.8 million years ago. However, the researchers argue that their findings illustrate a picture where early human ancestors potentially used the hot springs like a stewing pot to cook food. Though it's open to debate how they might have discovered this potential – had an animal fallen in? – or how they prepared their food, or even whether they boiled roots and tubers as well as meat.
The precise date of humanity’s “discovery” of fire is hugely disputed, but some of the most agreed-upon evidence says human ancestors used fire around 1 million years ago. While this theory of using hot springs to cook food over 1.7 million ago might be a stretch, the evidence of hot springs near human settlements raises the possibility that hominins might have had access to cooked food and much-needed nutrition long before we managed to master flames.