Man in Evolution: A Scientific Statement and Some Theological and Ethical Implications

THE THOMIST A SPECULATIVE QUARTERLY REVIEW OF THEOLOGY AND PHILOSOPHY EDITORS: THE DoMINICAN FATHERS OF THE PRoviNCE oF ST. JosEPH Publishers: The Thomist Press, Washington 17, D. C. VoL. XXXI JANUARY, 1967 No.1 MAN IN EVOLUTION: A SCIENTIFIC STATEMENT AND SOME THEOLOGICAL AND ETHICAL IMPLICATIONS* IN 1864, Thomas H. Huxley wrote that " The question of questions for mankind- the problem which underlies all others, and is more deeply interesting than any otheris the ascertainment of the place which man occupies in nature and of his relations to the universe of things. Whence our race has come; what are the limits of our power over nature, and of nature's power over us; to what goal we are tending; are the problems which present themselves anew and with undiminished interest to every man born into the world." In the Origin of the Species, published in 1859, Darwin indicated that * I am indebted to Professor Th. Dobzhansky and to Father J. S. McCormack, 0. P., who read an earlier draft of this paper and offered many valuable suggestions. I am, of course, solely responsible for any existing errors of omission or commission. Variants of this paper were presented at tlJ.e University of Toronto, on January 12, 1966, and at the University of Virginia on March 18, 1966. 1 FRANCISCO JOSE AYALA the theory of evolution would throw light on man's origin, and in his Descent of Man, published in 1871, he argued that man and apes share a common ancestry. Mankind is a biological species: it is a part of nature. Like other living things, man has evolved from humbler beginnings. Our not very remote ancestors were not human. The species Homo sapiens is of very recent origin when placed on the geological time scale. At the present time, the evolution of man from non-human ancestors is regarded as a well established theory by persons qualified to judge the relevant evidence. The main steps of that evolutionary development are known with reasonable certainty. Life originated on our planet some 8,500 million years ago. The first vertebrates appeared about 500 million years ago, and the first mammals about 400 million years later. The evolutionary line of descent giving origin to modern man separated from that of our closest animal relatives, the great apes, some 25 million years ago. The sequence of anatomical changes leading to modern man includes progressive development of bipedal locomotion, erect posture, greater flexibility of hand, a tongue and mouth cavity capable of emiting a greater variety of sounds, and a larger brain and brain case. The transition occurred probably in tropical Africa between 2,000,000 and 500,000 years ago. The Australopithecines, who lived during that period, are believed to be the early members of the family to which man belongs. The most advanced members of that group were toolmakers. The earliest members of the subfamily Homininae, undoubtedly men by all criteria, were of the species Homo erectus. Their fossil remains have been found in Java, China., Algeria, Tanganika and, as recently reported, in Hungary, near Budapest. They were not only toolmakers, but the use of fire and rock shelters had allowed some of them to extend their range beyond the tropics. The average brain size of Homo erectus was twice that of Australopithecus, which scarcely exceeded that of a gorilla. These early men were successful and widespread; they lived during the Middle Pleistocene times, MAN IN EVOLUTION 8 between 600,000 and 300,000 years ago. By the end of the Middle Pleistocene, men had evolved beyond the Homo erectus stage and included variable types constituting the stock from which emerged the two races of Homo sapiens, neanderthalensis and sapiens. The brain case of the Swanscombe skull, belonging t01 that group and more than 100,000 years old, had a capacity of 1,325 cc, close to the average in modern man. Neanderthal men were eventually replaced or absorbed by Homo sapiens sapiens, people of entirely modem type, the only group of man living on earth for the last 40,000 or 30,000 years. Evolution from near man to modern man, Homo sapiens, occurred, then, during a relatively short period of...