Human Evolution

HUMAN EVOLUTION S. L. WASHBURN* Over the last 25 years there has been remarkable progress in a wide variety of sciences. The impact of the new methods and understandings has brought major changes to the study of human evolution. In a very few years the whole framework of space, time, and the fossil record has been modified. Even the synthetic theory, which seemed so secure a few years ago, is challenged by the neutral theory, and Dobzhansky, Ayala, Stebbins, et al. state that the relative importance of natural selection and stochastic factors "remains the most important unsolved problem in our understanding of the mechanisms that bring about biological evolution" [1, P- 164]. The purpose of this paper is to sketch these developments and to stress that, in my opinion, they are not minor. In one sense the new inevitably builds on the old, and those who do not know history are bound to repeat the errors of the past. But, in a different sense, those who rely too heavily on the past are bound to make the old mistakes. It has not been easy for students of human evolution to escape from the history of their subject. Even today people look to anatomy to settle the problems of evolution. Molecular biology offers far more powerful methods and shows why anatomy could not solve the problem of man's place in nature. The early theories of human evolution were based on comparative anatomy and embryology. Pilbeam has described these theories as "fossil free" [2, p. 7]. There were either no relevant fossils or so few that they exerted little influence on the theories. For example, scientists could not decide whether the original Neanderthal skeleton was a fossil or the remains of a pathological modern human. Major scientists were on both sides of the debate, and it was not until a number of skeletons were found around the turn of the century that most scientists accepted the The author thanks Alice Davis for editorial assistance and the Wenner-Gren Foundation for Anthropological Research for support. *Department of Anthropology, University of California, Berkeley, California 94720.© 1982 by The University of Chicago. AU rights reserved. 003 1 -5982/82/2504-0308$0 1 .00 Perspectives in Biology and Medicine, 25, 4 ¦ Summer 1982 583 Neanderthal as a kind of human being. Even then Neanderthals were described as "uncouth," "repellent," "unattractive," and incapable of fine coordination of the fingers: certainly belonging to a separate species [3]. Elliot Smith and Boule, who shared these views, were leaders in the scientific study of human evolution, and it was many years before Cave and Straus [4] showed that the basic descriptions of the bones had been grossly distorted by the opinions of those describing them. The image of Neanderthal presented to the general public and repeated in book after book was far removed from the actual study of the bones, and it was the image of a primitive, unattractive, and undesirable creature that created the interest in Neanderthal. Hrdlicka's [5] calm description of "the Neanderthal phase of man" could not compete with Boule's dramatic reconstruction. The "fossils" of the 1920s were an odd lot. They included (and I am only considering specimens accepted by major scientists) genuine fossils, mistakes, fragments, fakes, and gross misconstructions. If the early studies had been "fossil free," they were followed by studies which were "nonsense rich." The most careful scientists could not tell which fossils were genuine and well enough preserved to be useful and which were simply misleading. The nonsense-rich era produced futile and often acrimonious debate. In our culture it is customary, when looking back, to consider who was right and who was wrong. Both the fossil-free and the nonsense-rich eras produced theories which were stoutly defended and can only be understood in terms of opinions of times long past. For example, how could anyone accept Piltdown, a modern braincase with an ape'sjaw? This seems impossible today, but wise scientists (Keith and Hooton) accepted it, and other wise scientists (Hrdlicka and Weidenreich) did not. Personal wisdom and scientific training were not enough to lead to useful debate, and the opinions of others were usually dismissed...