Washington: The immediate ancestor of humans may have lived almost exclusively on a diet of leaves, fruits, wood and bark instead of a menu based on the open savanna as other extinct relatives of humanity did, scientists claimed.
The findings, published in the journal Nature, are based on two million years old fossils of the extinct hominin Australopithecus sediba that were accidentally discovered by a scientist's nine-year-old son in a South African cave in 2008.
Au-sediba's mix of human and primitive traits has made a strong case for it being the immediate ancestor of the human lineage. Chimpanzees, humans' closest living relatives, prefer fruits and leaves even when grasses are abundant. By contrast, extinct species of humans apparently preferred diets richer in grasses or grass-eating animals.
The findings suggest there wasn't a single, straight line from an early, primitive hominin to humans, said study author Amanda Henry, a paleoanthropologist at Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany.
"Many of our ancestors and relatives branched out, tried new things and generally worked at doing what was best in their environment at that particular time," Henry was quoted as saying by LiveScience.
According to scientists, what our ancient relatives might have eaten can be gauged by studying their teeth, particularly the marks and remnants left on them by food.
This can also be known by looking at the carbon isotopes making up fossils; the grasses that dominate savannas engage a kind of photosynthesis that involves both normal carbon-12 and heavier carbon-13, while trees and shrubs rely on a kind of photosynthesis that prefers carbon-12.
In the latest study, by analysing two fossil specimens, the researchers found that the diet of Au-sediba apparently differed substantially from most of other extinct species of hominins studied so far.
Carbon isotopes from the remains suggest that Au-sediba ate nearly completely woodland diets, comparable to forest specialists such as giraffes. In addition, tiny fragments of a diverse range of plant tissues, including bark and wood, were found in the teeth of one of the remains.
"There is more variety in our past than we expected. We are seeing more variation among the diets and behaviours of early hominins than we'd previously seen," Henry said.
Henry and her colleagues are now looking for remnants of food stuck in the teeth of other extinct hominins.
First Published: Thursday, June 28, 2012, 16:13