Early Humans Were Roasting Tubers 120,000 Years Ago, Researchers Discover

Everyone loves starch, but we finally have proof from the South African coast that taste for it goes back to early human history, shedding some light on how our diet evolved

File photo: Potatoes are seen in a box at a company in Xylophagou village, Cyprus, February 25, 2019.
Yiannis Kourtoglou/Reuters

We all love a roast potato, the partiality for pasta is practically universal and now solid archaeological evidence has been found to prove that our predilection for starch goes into the dimmest reaches of human history.

Archaeologists excavating the Klasies River Caves on the South African coast have found the earliest known evidence of starch being roasted, around 120,000 years ago, Cynthia Larbey of the University of Cambridge and colleagues reported Wednesday in the Journal of Human Evolution.

What they found specifically was charred starch plant tissue (the internal part of the plant parenchyma) in cave and rock shelter hearths. In fact, people lived in these caves for at least 60,000 years and cooked starches and a lot of other things throughout, the archaeologists say.

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Organic tissues and substances from the upper hearth in Klasies River Caves, South Africa, under reflected and UV light.
C. Larbey

Authors suggest that their discoveries support one theory on human evolution, arguing based on genetics that Homo sapiens adapted to increased levels of starch when it became omnivorous.

The most recent thinking is that our earliest ancestors split from our brother the chimp about 6-7 million years ago. It bears saying that the earliest members in the Homo lineage are believed to have been vegetarian, or as Larbey put it: they had a forest diet. They probably wouldn’t scorn the occasional snack of dead bird or lizard, but they ate chiefly plants.

However, by the time Australopithecus was running around about three million years ago, in South Africa too by the way, our diet had taken am omnivorous turn, based chiefly on evidence of the teeth.

Our species, Homo sapiens, is now thought to have begun to evolve at least 300,000 years ago, going by startlingly modern remains found in Jebel Irhoud, Morocco in 2017. By that time, they would definitely eat anything that moved, didn’t move, or grew in the ground. 

The earliest evidence of occupation in the specific complex that is called the Klasies Caves dates to around 120,000 to 125,000 years ago, Larbey tells Haaretz – that is the very baseline of excavation in the caves. The hominins there were definitely Homo sapiens, if not yet fully anatomically modern human, she says: they still had some primitive traits. For instance, they still retained some sexual dimorphism in their teeth. “The differences were small. You might not notice them if they were walking down the street; but they are not quite there yet,” she says. 

In any case, while arguments rage fiercely about which hominins could control fire (meaning, ignite it, not just exploit it), and when – by the time early humans lived in the Klasies River Caves, with their sexually distinct teeth, they were cooking.

Roasting a quick lunch for the kids 

The recent paper relates to two periods of time in Klasies River Caves: 120,000 years ago and 65,000 years ago. In both cases, remarkably, the archaeologists found evidence of small hearths, only about 30 centimeters in diameter. The evidence indicates that these mini-hearths were used only for cooking, not for huddling around telling stories of the hunt. 

Perhaps the most remarkable aspect of these tiny hearths is that they didn’t change throughout the 55,000-year record (from 120,000 years to 65,000 years), and they also bear a strong resemblance to hearths that hunter-gatherers make to this day, Larbey says. 

It was in these tiny hearths that they found categorical evidence that the ancient humans had been roasting starch. Maybe they peeled the tubers and tossed the peels into the fire for extra fuel.

Researcher Cynthia Larbey walks to the mouth of one of the Klasies River Caves, South Africa, 2015.
C. Larbey

Larbey points out that the early humans would understandably have had a policy of waste not, want not. “They were pushing fuel back in to make sure everything was burned,” she said. Moreover, she points out that what they find is waste that dropped into the fire, or was pushed there, they wouldn’t have sacrificed a tuber that could be eaten so archaeologists could find it 120,000 years later. If they had it, they used it to the max.

“These were very small, ashy little hearths where they’re very functional, just cooking something quickly, sort of like the hob as opposed to the oven in modern cookery,” Larbey suggests. “If you gotta feed the kids something, and want to get to it quickly, you do it in this hearth here, but fold the fuel back in because it’s a pain to go out and get some more.”

In the small hearths, the archaeologists also found some small bones, from animals. Separately they found great roasting pits from the earliest times, for the likes of mega-fauna or even baby seals.

Which begs the question of what else they ate.  

Along the South African coast, the early humans were clearly exploiting marine resources, mainly shellfish. “They had huge middens (waste heaps) of seashells. It’s everywhere,” Larbey says. Middle Stone Age sites up and down the coast show the same. At Blombos Cave, there is some evidence that the early humans weren’t just collecting seashells on the seashore. They were diving for them. We can elucidate that from the presence of shells from deeper waters that wouldn’t be expected to be in these middens, she explains. 

Charred food remains from hearths in Klasies River Caves, South Africa.
C. Larbey

Now, from different seasons when they couldn’t collect seafood because of storms, the South African coast's notoriously treacherous tides and so on, they would eat things like Cape fur seals or penguins.

Cape fur seals are huge and there is a question of how they were obtained. One school of thinking is that the early humans scavenged dead ones, and dolphins too, that washed up on the beach. 

Larbey points out that it isn’t rare for “perfectly fresh” dead seals and penguins to wash up on the beach. Or there could be slightly more blood-curdling options. “You don’t need a particularly stormy day,” she says. “You get exhausted seals that just come ashore and sit there, and have a sleep. It’s foraging, to be honest, to club an exhausted seal.”  All in all, dead or tired animals on the beach were a pretty easy opportunity to exploit on a regular basis, she says.

The hearths date to periods when the cave sat right by the sea. However, during the human occupation of it, there were also glacial periods when sea levels were lower. Then the cave didn’t have a view of the sea, it had a view of the savannah and the occupants ate of the elephant, the rhino, buffalo and antelopes galore, going by bone findings. 

So, is this hearth from 120,000 years ago the first time starch was eaten? Not likely. 

Genetic analysis indicates that hominin starch digestion genes doubled around 300,000 years ago. Chimps and gorillas (which could be taken as akin to our earliest relatives) have the original ancestral set of two copies of the starch digestion genes, no more. 

The find of the starch being cooked 120,000 years constitute archaeological evidence – that had ben lacking until now – in support of the hypothesis that starch digestion genes were duplicated is an adaptive response to an increased starch diet, Larbey suggests. 

Excavation site at Klasies River, South Africa.
C. Larbey and D. Redhouse

Clearly, in any case, starch was being cooked and eaten well before agriculture began, which was around 10,000 to 20,000 years ago.

Today carbohydrates constitute between 55% to 80% of the modern human diet, according to global health authorities. Why? Because we love starch and it’s easier to produce than chicken nuggets. Is it good for us? Stay tuned. Maybe in another 120,000 years we will have a definitive answer for that.