Actually that's not my literature, I go to the scientific source material the vast majority of the time:
But why? Cladistical analysis is hardly a friend to the creationist, hence all the amusing controversy about what hominid fossils go where -- creationists have serious problems agreeing what constitutes an ape, a hominid (for those creationists who recognize such categories) or a human.
In the cases of newly discovered fossils, or when the species is known by highly fragmentary evidence, those who hold to the standard scientific paradigm have similar debates, but there's a lot less riding on it and some confusion is to be expected by the very nature of the evolutionary paradigm. It's a big problem for you guys, though.
Like humans, [apes and monkeys] go through stages as they grow up. In his analysis of Taung, Dart did not fully appreciate that infant apes have not had time to develop features of the skull, such as thickened eyebrow ridges or attachment areas for heavy neck muscles, that set adult apes apart from human. Apparently he did not carefully consider the possibility that Taung's rounded forehead or the inferred position of the spinal cord might be due to the immaturity of the apelike specimen rather than to its resemblance to humans (
Dean Falk, Braindance)
Seems a bit iffy to judge the entirety of modern anthropology based on the science of 1925. It seems that your view was indicative of the scientific consensus of the time. Now we have more Australopithecus fossils and better models, and the opinion is that
Dart had it right.
The ape skulls average well under 500cc while humans are right around 1350cc. Homo habilis had a chimpanzee sized brain, in fact every skull before Turkana Boy was chimpanzee sized. Turkana Boy on the other hand was identical to modern humans except for a slightly smaller skull.
Well that's not the whole story:
Comparison of Cranial Capacities
range (cm3) ----- average (cm3)
chimpanzees 300-500 ----- ----
australopithecines 390-545 ----- ----
Homo habilis 509-752 ----- 610
Homo erectus 750-1250 ----- 930
Homo heidelbergensis 1100-1390 ----- 1206
Neandertals 1200-1750 ----- 1450
modern Homo sapiens 900-1880 ----- 1345
Source
That's not what is happening here, there is no reason to believe that Taung is anything other then a chimpanzee ancestor. Until the demise of Piltdown Man that is exactly what it was considered. Raymond Dart, the discoverer of the taung child would be the one to suggest the name Homo habilis (handy man) to Louise Leaky. Leaky from a child believed that early man was proficient in tools after reading a child's book called 'Tigi, Stone Age Hunter. His sister would say later that it became his Bible really. (See Virginia Morell, Ancestral Passions).
I keep finding this at the unveiling of every ape skull unearthed. Not a single chimpanzee skull and yet we would have cohabitated equatorial Africa right up until about 1mya.
But you're ignoring the inconvenient yet indisputable truth that Chimpanzees live in heavily forested areas, and the fossil record of almost all forest dwellers is extremely patchy because of
acidic soils and many scavengers, so it's not at all likely that a good fossil record for modern chimps will ever become extant.
A. Afarensis with a cranial capacity of ~430cc lived about 3.5 mya.
A. Africanus with a cranial capacity of ~480cc lived 3.3-2.5 mya.
P. aethiopicus with a cranial capacity of 410cc lived about 2.5 mya.
P. boisei with a cranial capacity of 490-530cc lived between 2.3-1.2 mya.
OH 5 'Zinj" with a cranial capacity of 530cc lived 1.8 mya.
KNM ER 406 with a cranial capacity of 510cc lived 1.7 million years ago.
Then evolution makes this giant leap. The next link would have been Homo erectus with a cranial capacity of ~1000cc. KNM-WT 15000 (Turkana Boy) would have lived 1.5 mya and the skeleton structure shows no real difference between anatomically modern humans.
Not according to the information I previously cited, and that's information didn't include all the known hominids.
These supposed ancestors are never considered ape ancestors because they do not consider cranial capacity to be a basis for exclusion from the Homo clad. Louis Leaky called this the 'Cerebral Rubicon' and once crossing it there was no going back. Now every ape skull can be considered our ancestor. There is just one problem with that. The three-fold expansion of the human brain from that of apes had neither the time nor the means. That giant leap would have had to happen about 2mya and like every evolutionary giant leap has not genetic basis for it.
And why is that? Positive selection can be comparatively speedy in evolutionary terms. In fact, in the case of dogs, where the artificial selective pressures were quite extraordinary, there is as much variation in the shape of skulls as there is in the e
ntirety of Carnivora.
With a cranial capacity nearly three times that of the chimpanzee the molecular basis for this giant leap in evolutionary history is still almost, completely unknown.
Cranial capacity is a fairly rude indicator of intelligence, but I take your point. You might want to take a look at the MYH16, HAR complex and FOX-P. Some pretty swift evolution in HAR, but these genes are not protein coding, so it seems there was a bit more room for flex.
