Hominid Species Time Line

Page 8

Australopithecus anamensis

In 1994, remains of a new species, Australopithecus anamensis, was discovered in the Lake Turkana region of east Africa.  This species appears contemporary with A. afarensis or slightly older, dating to approximately 4.2-3.8 million years ago.  Until this time, Lucy’s species, A. afarensis, was the earliest known hominid species and member of the Australopithecine genus yet discovered.

Skeletal remains of A. anamensis preserve direct evidence of bipedalism somewhat earlier than 4 million years ago.  Contrary to previous assumptions, the evidence shows that these early hominids had developed upright walking prior to the disappearance of woodlands and forests in eastern Africa.  That is to say, our hominid ancestors acquired the ability to walk upright in a forest environment, not out on the savanna or in bush country. 

The earlier view had held that the drying out of the African continent, particularly in the eastern half, had provided the stimulus for the development of bipedalism.  That mode of locomotion apparently carried a significant advantage over knuckle-walking even in a forest environment.  In any case, that is where it developed.  The “how?” and “why?” are still open questions.

Because of these finds, it was established that bipedalism developed much earlier than previously anticipated, and it appears likely that it may have occurred in the central part of Africa rather than in the east.  Nevertheless, one aspect of the earlier hypothesis holds up.  When conditions in Africa did became drier and the forest retreated, bipedal hominid species had the physical “equipment” to move out and colonize the new environments. 

Our family history after 3 million years ago turns on this exodus from the forest.  Bipedal hominids, some of them descended from anamensis and perhaps others of different stock as well, moved out into the more open country in eastern Africa and by adapting to this more challenging environment, were forced to develop in new ways.

References:

Australopithecus anamensis on TalkOrigins.org