Washington, May 28 (ANI): Pre-humans living in East Africa 4.4 million years ago inhabited savannas, grassy plains dotted with trees and shrubs, according to a team of researchers.
This theory opposes another theory - that of Berkeley researcher Tim D. White - who said that early humans occupied forests as their natural habitat.
"Our team examined the data published by White and his colleagues last October and found that their data does not support their conclusion that Ardipithecus ramidus lived exclusively in woodlands and forest patches," said Naomi Levin of The Johns Hopkins University's Krieger School of Arts and Sciences.
The claim that the 4.4 million-year-old fossil nicknamed "Ardi" lived in woodlands and forest patches was used as an argument against a longstanding theory of human evolution known as the "savanna hypothesis."
According to that premise, the expansion of savannas prompted our ape-like forebears to descend from trees and begin walking upright to find food more efficiently, or to reach other trees for resources or shelter.
Levin's team used the White team's own data to draw very different conclusion about the environment inhabited by Ardi, an omnivorous, ape-like creature that stood about 4 feet tall and had a brain less than a quarter of the size of a modern day human's.
"If the habitat of A. ramidus was, in fact, a woodland with forest patches, where grasses were rare, then it's unlikely that the increased presence of grassy environments were the driving force behind the origin of upright walking in early human ancestors. However, if the habitat of A. ramidus included savannas where grasses were up to 60 percent of the available biomass, then we cannot rule out the possibility that open environments played an important role in human origins and, in particular, in the origins of upright walking. The scientific community and the public should not accept an exclusively woodland/forested habitat for A. ramidus and the origins of upright walking, because the data do not support it."
The critique concludes that although its authors do not judge the validity of the savanna hypothesis, the connection between human ancestors walking upright and the expansion of grasslands remains a viable idea.
The report is published in today's issue of Science. (ANI)