News Column

Human Ancestors Had Varied Diet: Texas A&M

July 5, 2012

Cassie Smith

A Texas A&M University paleoanthropologist says he was surprised by new findings on the diet of Australopithecus sediba, believed to be an early relative of modern-day humans.

Darryl de Ruiter, an associate professor in A&M's department of anthropology, said he and his international team of researches have discovered that Australopithecus sediba enjoyed a diet of leaves, fruits, nuts and bark, which meant they probably lived in a more forested environment than thought.

The team named the new species Australopithecus sediba and demonstrated that it displayed both human-like and ape-like characteristics shared with other forms of Australopithecus and modern-day humans.

"What was surprising was how different it was from what we know of other species in the region at roughly the same time," said de Ruiter, who was born in Canada and received his degree in South Africa, where he lived until being hired by Texas A&M nine years ago.

The team's findings were published in the current issue of Nature magazine. Its work was funded by the National Science Foundation, the Smithsonian Institution, the Institute for Human Evolution at the University of Witwatersrand in Johannesburg, the Ray A. Rothrock '77 Fellowship in the College of Liberal Arts at Texas A&M and the Max Planck Society.

Australopithecus is an extinct genus of hominins. They were ape-like yet walked similarly to modern humans. De Ruiter said they are considered to have played a significant role in human evolution. An analysis of phytoliths -- microscopic deposits found in plants that often get trapped in plaque on teeth -- suggested they had a varied diet.

The diet of early Australopithecus, he said, is central to the study of human origins. De Ruiter, 44, said the discovery revealed that the diet was almost entirely forest-based, similar to what modern chimpanzees eat today.

"Which is surprising and not surprising," he said. "It's not surprising because we share a common ancestry with chimpanzees. We still have a lot of dietary similarities with chimpanzees, even today. What is surprising, was how different it was from everything else we've seen though ... We are predominately grass eaters today. If you think of corn for instance, that's a grass, wheat is a grass, barley is a grass, we have to extensively process all of those before we can digest them. You can't just eat a cob of uncooked corn. It won't do you any good."

De Ruiter said the findings also illustrated that they had access to more food sources than previously established.

He said the team examined teeth from skeletal remains of a group of newly discovered hominins found in a South African cave. Material recovered from the teeth using such tools as dental picks and laser ablation devices was analyzed to determine what Australopithecus sediba was eating.

The fossils are housed in South Africa, where de Ruiter regularly travels to collect data, which he analyzes and writes up at Texas A&M.

Sedibas are dated to 1.977 million years ago, plus or minus 1,500 years, an "extraordinarily precise time frame," he said. However, he said, researchers don't know when the sediba first appeared or when they went extinct.

To date, they've only been discovered in South Africa, he said.

"I strongly suspect, and I have no evidence, that these guys were all over Africa," de Ruiter said.

Source: (c) 2012 The Eagle (Bryan, Texas)

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