Why are the australopithecus, neanderthal etc. not regarded as the intermediate human evolutionary forms?
Australopithecines *are* regarded as intermediate forms, just not all of them are regarded as being direct ancestors — the early hominid family tree was more like a bush. It’s just like your great-great-grandfather’s brother was not likely to be a direct ancestor of yours, but was still probably representative of his generation. Neanderthals are our cousins. They were contemporary with both Homo heidelbergensis and Homo sapiens sapiens with substantial periods of overlap for both, indicating that their line split from ours before modern humans existed. They have been fairly definitively excluded from our direct ancestry on the basis of genetics — mitochondrial DNA have been recovered from several Neanderthal skeletons and tested against human mtDNA for shared sequences. It was demonstrated that the mtDNA lines had diverged from each other significantly, and that the Neanderthal mtDNA had sequences that we would expect to find in Homo sapiense sequences if they were ancestral to us —
Neanderthal man is no longer considered a direct ancestor of man because a specimen was found which contained enough DNA fragments to do mitochondrial DNA analysis and it was concluded that it was not a direct ancestor of man from the results of this analysis. Australopithecus is still considered by some to be a direct ancestor, but there is some debate over this point. There are two types of Southern Ape, the robust and the gracile. The robust one has been discarded by most as an intermediary species, while the gracile one is still thought to be an ancestor. There are those that are termed lumpers, though, who think that there is great deal of variation within a species and would group the gracile and robust forms together as one species becasue of the similarities, which is why they are placed in the same group, Australopithicus. If a lumper were to say the robust form is not a direct ancestor and continue to see the gracile and robust forms as one group, he would also discard the gr
