Hominid evolution and the evolution of the environment
Yves Coppens
African Apes being our closest relatives, it is reasonable to
think that we have with them a common ancestor. As the earliest hominids were found,
without any exception, in the eastern, in the eastern part of Africa, as the African Apes
are living in the western part of equatorial Africa and as absolutely no remain of fossil
Ape has been found in the eastern part of equatorial Africa, in contemporaneity with the
Hominids, it is reasonable to think that the common ancestor has been living across the
whole equatorial Africa and that its descendance has been divided.
As the Rif Valley, as a matter of fact, is dividing equatorial
Africa into two parts, an eastern one and a western one, it is reasonable to think that it
has been the sinking of the Rift and the uplifting of its western wall which have been the
reason of a different ecological history on each side of the Rift, forest on the west,
savannah on the east, and the reason of a different destiny of the descendants of the
common ancestor on each side as well, Apes in the west, Hominids in the East. This event
may have happened in the upper Miocene, 8 to 10 million years ago (The East Side Story).
Two severe droughts followed, the first one, 4 million years ago,
probable reason of the expansion of savannah and of Australopithecines towards the south
and the west (The crossing of the Rift), the second one, 3 million years ago, probable
reason of the emergence of Homo (The (H)Omo event).
As soon as (geologically speaking) Homo emerged, he moved,
reaching Eurasia 2.5 million years ago. In two million years he became modern everywhere
in this old world, except in Europe and in Indonesia where he became, respectively,
Neanderthal and Pithecanthropus because of isolations of these areas and consecutive
genetic drifts (Out of nowhere model).
The last movement, 50 thousand years ago, was a movement of Homo
sapiens towards the places where he has not traveled, towards America and Oceania,
empty, Europe (Cro Magon) and Indonesia (Wadjak) already peopled (The world citizenship).
