Early Human Ancestors Ate Grass

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Early human ancestors in central Africa 3.5 million years ago ate a diet of mostly tropical grasses and sedges, finds new research.

The study suggests our relatives were mostly plant-eaters before they evolved a taste for meaty flesh. Consider that tidbit while passing around the creamed spinach during Thanksgiving dinner.

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The study focused on Australopithecus bahrelghazali, which had quite a set of teeth. You can see a reconstruction of this human relative here.

“We found evidence suggesting that early hominins, in central Africa at least, ate a diet mainly comprised of tropical grasses and sedges,” co-author Julia Lee-Thorp, a University of Oxford archaeologist, said in a press release.

She continued, “No African great apes, including chimpanzees, eat this type of food despite the fact it grows in abundance in tropical and subtropical regions. The only notable exception is the savannah baboon which still forages for these types of plants today. We were surprised to discover that early hominins appear to have consumed more than even the baboons.”

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She and her colleagues made the determination after studying the fossilised teeth of three A. bahrelghazali individuals — the first early human relatives excavated at two sites in Chad. The researchers analyzed the carbon isotope ratios in the teeth and found the signature of a diet rich in foods derived from C4 plants.

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This indicates our long-gone relatives experienced a shift in their diet relatively early, at least in central Africa. These individuals survived in open landscapes with few trees, so apparently they could exploit not only dense woodland areas but also other environments.

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Although the area where A. bahrelghazali roamed is now dry and hyper-arid, back in the day it featured a network of shallow lakes with nearby floodplains and wooded grasslands.

While this ancestor of ours clearly had big, impressive teeth, they would not have been able to tackle leaves day after day. The individuals also lacked cow-like guts to break down and digest such food, so the researchers suspect the early hominids probably relied more on the roots, corms and bulbs at the base of the plants.

Given the carbon isotope data, there is a very remote chance that the early hominids ate animals that, in turn, ate the tropical grasses.

“But as neither humans nor other primates have diets rich in animal food, and of course the hominins are not equipped as carnivores are with sharp teeth, we can assume that they ate the tropical grasses and the sedges directly,” Lee-Thorp said.

The research was published in Proceedings of the National Academy of Sciences.

(Image: J.M. Garg)