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Early Human Diet Went Grassy

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A dietary link to standing on two legs, big brains

anthropology, humans, diet, evolution, University of UtahModern apes eat mostly fruits and leaves in heavily wooded forests. Until recently, scientists believed that early human ancestors shared this diet. But a series of studies from the University of Utah found that our ancestors expanded their culinary tastes to grasses and grains, as much as 3.5 million years ago.

The findings are important because they show a shift in diet among human ancestors, at about the same time they were moving from forests into grasslands and savannahs—new environments that were conducive to upright walking. Once accustomed to walking upright, human ancestors then began developing fine motor ability, bigger brains and all the other factors that make us, us.

The researchers used isotopes of carbon found in fossilized teeth dating between 10,000 and 4 million years ago. At about 3.5 million years, the data showed an increase in grassy material. The scientists—and we—still don’t know if grass was the only part of the new human diet, or if they were also eating insects, meat or fish. Meat scavenging doesn’t appear in fossil records until 2.5 million, and hunting dates only 500,000 years ago. But it looks like the stage was set for at least part of our modern diet a lot earlier than we assumed, and that our diet may have influenced how we became human.

Source: University of Utah

Photo: University of Utah

Cerling TE, Manthi FK, Mbua EN, Leakey LN, Leakey MG, Leakey RE, Brown FH, Grine FE, Hart JA, Kaleme P, Roche H, Uno KT, & Wood BA (2013). Stable isotope-based diet reconstructions of Turkana Basin hominins. Proceedings of the National Academy of Sciences of the United States of America PMID: 23733966

Wynn JG, Sponheimer M, Kimbel WH, Alemseged Z, Reed K, Bedaso ZK, & Wilson JN (2013). Diet of Australopithecus afarensis from the Pliocene Hadar Formation, Ethiopia. Proceedings of the National Academy of Sciences of the United States of America PMID: 23733965

Sponheimer M, Alemseged Z, Cerling TE, Grine FE, Kimbel WH, Leakey MG, Lee-Thorp JA, Manthi FK, Reed KE, Wood BA, & Wynn JG (2013). Isotopic evidence of early hominin diets. Proceedings of the National Academy of Sciences of the United States of America PMID: 23733964

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