Paranthropus boisei, an early hominin that lived in East Africa between 2.3 and 1.2 million years ago, mainly ate tiger-nuts – edible bulbous tubers of the sedge Cyperus esculentus (also known as nut grass, chufa sedge, yellow nutsedge or earth almond), according to a new study involving modern-day baboons. The study, conducted by Oxford University scientist Dr Gabriele Macho, suggests that this hominin may have sought additional nourishment from fruits and invertebrates, like worms and grasshoppers.

Anthropologists have debated for almost five decades why Paranthropus boisei had strong jaws, indicating a diet of hard foods like nuts, yet their teeth seemed to be made for consuming soft foods.

Previous studies suggested their diet was largely comprised of grasses and sedges. However, a debate has raged over whether such high-fiber foods could ever be of sufficiently high quality for a large-brained, medium-sized hominin.

Dr Macho examined the diet of Paranthropus boisei through studying year-old Yellow baboons (Papio cynocephalus) in Amboseli National Park in Kenya – a similar environment to that once inhabited by the ancient hominin.

The scientist found that baboons today eat large quantities of tiger-nuts. This food would have contained sufficiently high amounts of minerals, vitamins, and the fatty acids that would have been particularly important for the hominin brain.

The study, published in the open-access journal PLoS ONE, is based on the assumption that Yellow baboons intuitively select food according to their needs. It concludes that the nutritional demands of Paranthropus boisei would have been quite similar.

“I believe that the theory – that Paranthropus boisei lived on large amounts of tiger-nuts – helps settle the debate about what our early human ancestor ate. On the basis of recent isotope results, these hominins appear to have survived on a diet of C4 foods, which suggests grasses and sedges. Yet these are not high quality foods,” Dr Macho said.

“What this research tells us is that hominins were selective about the part of the grass that they ate, choosing the grass bulbs at the base of the grass blade as the mainstay of their diet.”

Tiger-nuts, which are rich in starches, are highly abrasive in an unheated state. Dr Macho suggests that Paranthropus boisei‘s teeth suffered abrasion and wear and tear due to these starches.

The study shows that baboons’ teeth have similar marks giving clues about their pattern of consumption.

In order to digest the tiger-nuts and allow the enzymes in the saliva to break down the starches, Paranthropus boisei would need to chew the tiger-nuts for a long time. All this chewing put considerable strain on the jaws and teeth, which explains why the hominin had such a distinctive cranial anatomy.

Paranthropus boisei could extract sufficient nutrients from a tiger-nut-based diet, i.e. around 10,000 kilojoules (2,000 calories) a day – or 80 percent of their required daily calorie intake, in 2.5 to 3 hours. This fits comfortably within the foraging time of five to six hours per day typical for a large-bodied primate.

“Tiger-nuts, still sold in health food shops as well as being widely used for grinding down and baking in many countries, would be relatively easy to find. They also provided a good source of nourishment for a medium-sized hominin with a large brain. This is why these hominins were able to survive for around one million years because they could successfully forage – even through periods of climatic change,” Dr Macho concluded.

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Macho GA. 2014. Baboon Feeding Ecology Informs the Dietary Niche of Paranthropus boisei. PLoS ONE 9 (1): e84942; doi: 10.1371/journal.pone.0084942

* Sci-News.com would like to thank the artist Roman Yevseyev (www.other-worlds.ucoz.ru) for the incredibly realistic reconstruction of Paranthropus boisei.