Thoughts on the whole course of human evolution
Wu Rukang
1995, 14(04):
285-296.
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Most papers on paleoanthropology are devoted to the descriptions of certain human fossil finds or to a certain stage of human evolution, but very few concerns the whole course of human evolution. Here I try to present my thoughts on it with the following sections:
1 The transition from ape to human
I proposed in 1970's that there exists a transitional period from ape to human. The distinctive human traits arise successively in this period and no one single trait can be considered as the marker between ape and human. Here I will further elaborate this idea.
This period begins with upright posture and ends with the making of tools, the human society formed alongside. Self-consciousness and speech conceived before the tool-making. The creature of this period or "pre-human" can walk upright, constantly use natural wood sticks or stones to get foods and defend itself, leads a life of primitive social group with promiscuous sexual relations. In classification, they belong to the family Hominidae.
2 Punctuated equilibria or gradual evolution
Whether human evolution follows the models of punctuated equilibria or phyletic gradualism? It is an interesting question.
It is generally recognized that the course of human evolution starts from the pre-human (represented by the Australopithecine fossils) to Homo habilis, then to Homo erectus and finally to Homo Sapiens. The transition from A. afarensis to H. habilis is marked by considerable morphological continuity. The latest A. afarensis is 3 million years and the earliest Homo habilis is 2.4 million years old. No fossils had been found in the interval of 0.6 million years, but it can be inferred that this is the period for the changes of A. afarensis into Homo habilis. It seems to be an example of stasis and punctuation.
The earliest Homo erectus so far found in the Old World is a little less than 2 million years old. Their interrelations are not clear yet. They seem to have appeared almost abruptly and lasted very long time until 200,000 years ago. During this long period, they changed very little in morphology. Their implements also improved little. No significant trends can be observed and that stasis had occurred for over a million years before rapid evolutionary change began toward the end of the Middle Pleistocene.
3 Unbalanced development of physical features in human evolution
When I reviewed the physical features of Peking Man or Peking Homo erectus in 1960, I pointed out the unbalanced development of physical features in the course of human evolution and put forward an explanation (Woo Ju-Kang, 1960).Peking Homo erectus can already adopt an erect posture, has limbs and trunk fundamentally similar to those of modern humans, but with a somewhat ape-like head. As to the limb bones, the upper extremity is almost identical with that of modern humans, while the lower extremity, though similar to that of modern humans, still possesses some primitive characters.
The physical features of Peking Homo erectus may be simply and figuratively said to have a body like that of modern human combined with a primitive and somewhat ape-like head.
Not only the Peking Homo erectus is such a queer character, but the other early hominids also have similar forms.
How to explain these phenomena?
It is interesting to note that the principle of the mosaic mode of evolution is also applicable to the transition from the ape to human. Australopithecus, Homo habilis and Homo erectus all show mosaic features of modern humans and modern apes.
The upper extremity differentiates first and foremost toward the direction of modern human. Owing to the manipulation of the hands, the upper extremity differentiates faster than the lower one and hence the latter lags behind the former in the development toward the direction of modern human. The differentiation of extremities is followed by the development of the brain and the brain case, so the skulls and jaws still retain many primitive characters. The big brain of modern human is achieved in the long process of using and making of tools.
The process of human evolution demonstrates that, due to the constant use of hands for production, the extremities differentiate earlier than the development of brain. In western countries many people still believe that the swift advance of civilization was ascribed to the mind, to the development and activity of the brain, and mind is the motive force in human evolution. This idealistic outlook is refuted by the foregoing facts.
4 Evolution of modern humans
In human evolution, it generally deals with how early humans were evolved to modern humans, and did not touch the problem of the evolution of modern humans. Is modern humankind still evolving? If so, how is it evolved?
In 1990, I sugested that the evolution of modern humankind was expressed in two aspects: the extra-body evolution and the spiritual evolution. I elaborated it further in this paper.
