THESE are startling claims. Inasmuch as the theories of early man current in the scientific world are diametrically opposed to any reasonable literal interpretation of the Genesis account of human origins, the assertion that these theories must be "tossed out" is bound to capture the attention of conservative Christians.
The originator of these statements is the son of the famed paleoanthropologist, the late Louis B. Leakey. Young Leakey is continuing his father's search for early man. His search has been concentrated around the shores of Lake Rudolf in Kenya, some 500 miles north of Olduvai Gorge, where his father's most famous finds were made. In the past five years young Leakey reports finding fragments of eighty-seven individuals. Some of these he interprets as early man himself, others as close relatives. It is skull 1470, found in the 1972 field season, that should, according to Leakey, alter scientific theories of early man.
To understand the basis of these claims for skull 1470 and how the claims should be evaluated necessitates a bit of historical perspective on the search for early man.
Although Darwin gingerly tip-toed around the issue in his epoch-making work of 1859, The Origin of Species, it was soon apparent that Darwin did not in tend to exclude the origin of man from an evolutionary interpretation. The search for the "missing link" was on. The importance of this search was keenly felt because there was hardly any fossil evidence for human evolution.
The general acceptance of Darwinian theory led to the expectation of finding transitional types of fossil man. Since man's perceptions are so often colored by his expectations, it is not surprising that so-called missing links were soon found. Indeed, the expectations created by the widespread acceptance by scientists of the evolutionary interpretation of the origin of man contributed to certain unfortunate episodes in the history of anthropology. One was the thoroughly distorted picture of Neanderthal Man that was long promoted. We now realize that the brutish, hairy, semi-erect, ape like image of Neanderthal Man promulgated by a generation of anthropologists bore more resemblance to their expectations of what a missing link should be like than to the reality that could be inferred from the actual skeletal remains.
And, of course, it wasn't until 1953 that the so-called Piltdown Man skeleton was thrown out of anthropology's closet. Its long acceptance as an authentic fossil find derived primarily from the fact that the hoaxster was clever enough to make it conform precisely with anthropologists' expectations of what a missing link would be like.
However, the Piltdown episode has another side. It also illustrates the self-correcting capability of the scientific enterprise at its best. The accumulation of new data and the resultant changes in anthropological interpretations caused anthropologists to re-evaluate the authenticity of Piltdown Man. Using techniques derived from the physical sciences, anthropologists were able to establish once and for all that Piltdown Man was a fraud a combination of human and ape bones.
Neither Neanderthal Man nor Piltdown Man turned out to be genuine missing links. For many years following publication of Darwin's Origin of Species even supporters of Darwin had to admit there was a puzzling lack of transitional ape-man fossils. The evolutionary view of human origins rested on free-floating faith. It is true that during this period the Dutch physician Dubois introduced Java Man to the world. A few other similar specimens have been discovered over the years and today this group of fossils is classified as Homo erectus. Homo erectus seems to differ from present-day varieties of man only in certain features of the skull. Homo erectus did lend impetus to evolutionary interpretations of human origins because of the somewhat smaller absolute size of the brain as indicated by the cranial capacity of these specimens. The average cranial capacity of the very small sample of Homo erectus is within the range of normal modern men, but at the lowest end of that range. Some individual specimens possess cranial capacities below the normal modern range. Still, by any reasonable criterion, Homo erectus was probably fully human and, despite the features interpreted as "primitive," not the sought-after missing link.
Oddly enough, when the first finds of the creatures now thought by most anthropologists to be the long-sought transitional forms were announced by Raymond Dart, of South Africa, in 1924, his announcement was greeted with nearly universal skepticism. Professional jealousies certainly contributed to this skepticism, but a major factor was that man first evolved his large brain and that this then led to the emergence of the other distinctively human features. Piltdown Man conformed fully with this expectation with its human brain case and chimpanzee jaw. Dart's fossil find, which he dubbed Australopithecus ("Southern Ape"), had a brain no bigger than that of some living great apes, but possessed other physical features that were more manlike in appearance.
As is so often the case, after an initial dramatic discovery creates the expectation of success and the motivation for intensive search, the dam breaks and a flood of finds follows. By 1971,1,427 pieces of Australopithecine bone had been found. Most of these came from five South African limestone cave sites. 2
In East Africa, Louis Leakey's years of patient grubbing in Olduvai Gorge finally paid dramatic dividends in 1959 with the widely heralded "first man," Zinjanthropus boisei. Most scholars now feel that Zinjanthopus is just another Australopithecus specimen similar to some of the South African finds. A number of additional discoveries soon followed in Olduvai Gorge. Other areas of the East African rift valley system were also explored. Major finds were made in the Omo Valley by French and by American expeditions, and on the eastern margins of Lake Rudolf by Richard Leakey.
Actually, to talk of 1,427 bone fragments gives a distorted impression of the size and adequacy of the sample of Australopithecine fossils. One thousand and forty-three of these specimens are isolated teeth. 3 In fact, there isn't one complete Australopithecine skeleton, and an attempt to put together a complete skeleton from all the available bones would fail because some of the skeletal elements are unrepresented in existing collections. Another problem is the fact that it is usually impossible to associate with complete certainty cranial and postcranial remains. One has to assume that because the finds come from the same cave or the same rock outcrop that the cranial and post-cranial remains belong to the same species.
After the initial swell of skepticism had run its course, anthropologists came to accept the Australopithecines as man's ancestors. Recently it has been hard to detect the faintest echo of the initial skepticism that greeted Dart's announcement. A general consensus has arisen that some of the Australopithecines were certainly on the direct line of human evolution. The author of one of the most re cent textbooks on physical anthropology concludes his discussion of the Australopithecines with this comment: "Discovery of early specimens of Australopithecus are important because ... at least the early members of the genus must have been directly ancestral to man." 4
This interpretation of the Australopithecines has been quite satisfying to anthropologists be cause it supports the evolutionary hypothesis of human origins and fills in what had been a yawning gap in the evidence.
What is it about the Australopithecines that has led to the "ape-man" interpretation? The features that are interpreted as manlike relate primarily to the chewing and locomotor mechanisms. Dart's conclusions in 1924 were based largely on evidence related to the chewing mechanism. Compared to living apes, the jaw of Dart's new fossil was relatively smaller and lighter; the shape of the tooth rows was parabolic as in man, instead of more rectanguloid as in the apes; and there was no evidence for the large canines (the "eye-tooth") present in the males of living great apes. Other points were made, but these were some of the most obvious areas of similarity to man.
With the accumulation of more fossil material another dramatic tie with modern man was increasingly emphasized the interpretation of Australopithecine locomotion as bipedal. In other words, the Australopithecines were said to have walked about on two legs like man. This picture of Australopithecus as a biped rests upon inferences drawn from a number of skeletal features. These include the following: (1) The location of the foramen magnum (the hole under the skull where the spinal cord attaches to the skull). In man the skull is essentially balanced over the spinal column. As a con sequence the foramen magnum is located farther under the skull than on a quadruped skull. (2) The curvature of the lumbar area of the spinal column. It is claimed this curvature is demanded by an upright posture but is not necessary in a quadruped. (3) The shape of the pelvic bones. The upper part (ilium) is splayed out and does not have the elongation typical of the apes. The socket for the thigh (the acetabulum) is proportionately as large in the Australopithecines as in man and larger than that of any living primates.
The shape of the pelvic bones is certainly functionally related to type of posture. All in all, it is the nature of the pelvic bones that provides the most striking evidence for an upright posture in the Australopithecines. Yet, the number of complete pelvic bones is very small (there were only three known ilia in 1971) and, lacking a complete skeleton, there is no proof yet of their association with the Australopithecine skulls. Obviously, this point should not be pressed too far since it is based on negative evidence.
At the present time there is no positive evidence that can be used to controvert the contention that the known hip bones do not come from the same species represented by the skulls. It is still possible, but not probable, that the assumed association of skull and hip bones is not valid. One of the fundamental tenets of scientific research is to go with, not against, the odds. Nevertheless, the odds can change as new information and new ways of looking at old information come to the fore. Therefore, it is never wise to completely ignore possibilities in the search for scientific probabilities.
The presumed similarities to man seen in the Australopithecines are supposedly counter balanced by certain apelike attributes. These include such things as the lack of a chin, the practically nonexistent forehead, and the small brain. The cranial capacity of the Australopithecines was apparently very close to that of living apes. It is impossible, of course, to make any direct correlation between brain size and intelligence. We do not test for IQ by measuring cranial capacities! Nevertheless, the fact that the brains of the Australopithecines were basically ape-sized must have significance.
The consensus among anthropologists concerning the general evolutionary position of the Australopithecines does not extend to an interpretation of the variation present in Australopithecine collections. At least two different types have been recognized: A more "robust" type, Australopithecus robustus, slightly smaller than modern man; and a "gracile" (smooth) type, Australopithecus africanus, perhaps less than four feet tall and weighing only 40-50 pounds. Many anthropologists think the smaller type was man's ancestor and that the larger more robust type was an evolutionary side-branch that became extinct. Others have argued that the robust type evolved from the "gracile" type. And still others, a small minority, interpret the robust type as the male and gracile type as the female of one species.
A third type, presumably some what more similar to man, replaced Zinjanthropus in Louis Leakey's affections after it was discovered that Zinjanthropus was really not much different from the South African robust Australopithecines. Louis Leakey named his new contender for "earliest man" Homo habilis ("Capable man"). Many other anthropologists, though, feel that Homo habilis is really but a variant of the gracile type of Australopithecine previously known from South Africa.
The significance of the differences between these various types of Australopithecines has been hotly debated for many years. The debate shows no signs of being settled to everyone's satisfaction in the immediate future. The important point for our purposes is that despite this disagreement there is general unanimity in the belief that at least one of these Australopithecines was involved in what has been called "the African Genesis." As a result, Australopithecus has been given prominent billing in textbooks and popular works on science as "a" if not "the" missing link.
The anthropological consensus and the popular press have combined to create for many people a sense of complacent certainty about the standing and significance of the Australopithecines that may not be justified. The essential fragility of the evidence can easily be overlooked. This fragility involves the fragmentary nature of the fossil finds; the difficulty of associating cranial and post-cranial remains; the lack of even one complete skeleton; the still inadequate although rapidly growing sample; and the extent to which dependence must be placed on negative evidence. It is fair to say that the evidence is still sufficiently fragile that one or two key finds could lead all current interpretations to self-destruct in a matter of months.
The question is, Has Richard Leakey made such a find at Lake Rudolf? Does his find make it necessary, as he puts it, to "toss out current theories of early man"? It is to this question that we will turn in the concluding portion of this article.
(To be continued)
FOOTNOTES
1. Richard E. Leakey, National Geographic, June, 1973, p. 819.
2. Maitland H. Edey, The Missing Link, a volume from the Time-Life series, "The Emergence of Man" (New York: Time-Life Books, 1972), p. 46.
3. Ibid.
4. Gabriel Ward Lasker, Physical Anthropology (Holt, Rinehart and Winston, Inc., 1973), p. 258.
