Early human diet shows surprises

Darryl de Ruiter, associate professor in the Department of Anthropology, says the new findings are in contrast to previously documented diets of other hominin species and suggests that Australopithecus sediba had a different living environment than other hominins in the region. Previous research had shown that the australopiths of South Africa lived in the vicinity of grassy and open savannah-like areas, though it was unclear whether they actually occupied a savannah habitat, or if they lived in forested margins near the grasslands.

The team examined teeth from skeletal remains of a group of newly discovered hominins found several years ago in a South African cave about 30 miles northwest of Johannesburg and dated to about 1.98 million years old. The team, composed of researchers from the United States, Africa, Europe and Australia, named the new species Australopithecus sediba and demonstrated that it displayed a mosaic of both human-like and ape-like characteristics shared both with other forms of Australopithecus and with modern-day humans.

"By examining material recovered from their teeth using diverse tools ranging from dental picks and laser ablation devices, we were able to determine precisely what they were eating," de Ruiter explains.

"This gives us a very clear picture of their diet, and it was surprising. It shows that they ate more fruits and leaves than any other hominin fossil ever examined, more like what a chimp might eat. There was no evidence of them eating native grasses of the area at that time, which is what we see in other australopiths in the region."

Australopithecus is a genus of hominins that is now extinct. Ape-like in structure, yet walking bipedally similar to modern humans, they are considered to have played a significant role in human evolution, and it is generally held among anthropologists that a form of Australopithecus eventually evolved into modern humans.

The Texas A&M anthropologist says the analysis of phytoliths -- structures found in plants that often get trapped in plaque on teeth -- alongside examination of the chemical makeup of the hominin teeth, suggests that they had a varied diet, and diet of early Australopithecus is a key component central to the study of human origins.

"It shows they had a diet more similar to that of a chimp than anything else," he notes, "though we cannot yet say how much overlap existed between the diets of hominins and chimps.

"They ate fruits, tree bark, nuts, leaves, and sedges, plants such as papyrus or cypress. They might also have consumed some type of animal protein, perhaps in the form of insects or meat, but a lot more research will be required before we can say for sure one way or the other.

"Our findings clearly show they had access to more food sources than we had previously established," he notes.

The team's 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.