Abstract
A previous article outlined the new fossil evidence on man's origins recovered from East Africa and Ethiopia. Two problems raised by these fossil finds are discussed here.
The first concerns the evolutionary relationship obtaining between Australopithecus and Homo. The claimed coexistence between australopithecines and early forms of the genus Homo has sometimes been regarded as proof that the former could no longer be regarded as ancestral to the latter. More recent finds in Laetolil and Hadar, however, suggest that an early australopithecine form may have been ancestral to both later australopithecines and early species of Homo. This interpretation is compatible both with the traditional view that sees Australopithecus as ancestral to Homo and with the claimed coexistence of australopithecines with more advanced hominids.
The second problem here considered has to do with the coexistence at a number of sites in East Africa, for longer periods of time, of several distinct hominid lineages. Such coexistence is best documented in Omo, East Turkana and Olduvai. The most parsimonious interpretation of the fossil finds recognizes the coexistence of two distinct hominid lineages, one fairly uniform and perduring unchanged for over 1 million years (the robust australopithecines), the other comprising a variety of more gracile hominids. The large range of variation of the latter lineage creates as yet unsolved problems for the taxonomist, but it is apparently out of this variety of more gracile hominids that emerged Homo erectus whose appearance seems to have been the principal factor that occasioned the extinction of the robust australopithecine lineage.
