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Early Ancestors Fed on Tropical Plants and Sedges, New Study Shows

Dec 17, 2012 02:16 AM EST
Tropical grass

(Photo : Reuters)

Early ancestors in Africa fed on tropical plants and sedges between 3 million and 3.5 million years ago, reveals a new study.

A team of international researchers led by Oxford University examined the fossilized teeth of three individuals of the group Australopithecus bahrelghazali - first early fossil hominins that were discovered at two sites in the Djurab desert in Chad, Central Africa. The fossils date back to around 3.5 million years ago. The Djurab desert region, which is now a dry and arid environment, may have once had reeds and sedges that grew around shallow lakes and wooden plains.

The research team analyzed the carbon isotope ratios in the teeth and found a diet rich in foods derived from C4 plants.

"We found evidence suggesting that early hominins, in central Africa at least, ate a diet mainly composed of tropical grasses and sedges," Lee-Thorp, a specialist in isotopic analyses of fossil tooth enamel, from the Research Laboratory for Archaeology and the History of Art, said in a statement.

"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," he said.

The findings of the study suggest how early humans moved out of ancestral forests and woodlands to explore new environments. They managed to survive in open landscapes with fewer trees rarther than sticking to terrain that had more trees.

Earlier studies have suggested that early human ancestors possessed tough tooth enamel and large grinding teeth that helped them feed on food items like nuts and seeds. However, the new study suggests that early hominins diverged from the standard ape at an early stage.

Their teeth was not as sharp as carnivorous animals, suggesting that the hominins could not have eaten leaves from tropical grasses, as they are rough and not easy to digest. Instead, the hominins may have consumed roots and corms that are present at the base of the plants, said the researchers.

The study concludes that the diet of hominins possibly included animals, which in turn, fed on 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 findings of the study, "From the Cover: Isotopic evidence for an early shift to C4 resources by Pliocene hominins in Chad", are published in the journal of the Proceedings of the National Academy of Sciences.

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