London: A new study has challenged a long-held theory that our ancestors evolved to walk on two legs to help them see farther on Africa`s vast open grasslands.
For many years, it has assumed that our ancestors began walking upright as a response to savannah encroaching on shrinking rainforests in northeast Africa.
The theory claimed that human ancestors began walking to get around as there were fewer trees to swing from and walking on two legs enabled them to see predators and prey further afield, according to the Daily Mail.
But now a new analysis of the past 12million years` of vegetation change in north-east Africa has raised question on the long-held beliefs. about the world in which our ancestors took shape - and, by extension, the impact it had on them
It found that while the shift to bipedalism seems to have occurred somewhere between 4million and 6million years ago, rainforests had been replaced by grasslands and seasonally dry forests some time before 12million years ago.
Not only that, the tropical grasses and shrubs of the modern African savannah began to dominate the landscape earlier than thought, replacing other kinds of grasses better suited to a wetter environment.
As part of the study, Sarah Feakins, of the University of Southern California, investigated what types of vegetation dominated the landscape surrounding the African Rift Valley.
The area, which includes present-day Kenya, Somalia and Ethiopia, is where early hominin fossils trace the history of human evolution.
By combining sediment core studies of the waxy molecules from plant leaves with pollen analysis, Dr Feakins was able to investigate plant molecules dating back to between 12million and 1million years ago.
She then cross-referenced her findings with Naomi Levin, of Johns Hopkins University, who has compiled data from ancient soil samples collected throughout eastern Africa.