The Geotimes paper says other research has shown the Kenyan part of the wall rose mostly between 7 million and 2 million years ago, mountains in Tanganyika and Malawi were uplifted mainly between 5 million and 2 million years ago, and the walls southernmost end gained most of its elevation during the past 5 million years.
Clearly, the Wall of Africa grew to be a prominent elevated feature over the last 7 million years, thereby playing a prominent role in East African aridification by wringing moisture out of monsoonal air moving across the region, the Ganis write. That period coincides with evolution of human ancestors in the area.
Royhan Gani says the earliest undisputed evidence of true bipedalism (as opposed to knuckle-dragging by apes) is 4.1 million years ago in Australopithecus anamensis, but some believe the trait existed as early as 6 million to 7 million years ago.
The Ganis speculate that the shaping of varied landscapes by tectonic forces lake basins, valleys, mountains, grasslands, woodlands could also be responsible, at a later stage, for hominins developing a bigger brain as a way to cope with these extremely variable and changing landscapes in which they had to find food and survive predators.
For now, Royhan Gani acknowledges the lack of more precise timeframes makes it difficult to link specific tectonic events to the development of upright walking, bigger brains and other key steps in human evolution.
But it all happened within the right time period, he says. Now we need to nail it down.
|Contact: M. Royhan Gani|
University of Utah