AUSTRALOPITHECUS AFARANSIS AND THE CREATIONISTS
by Lenny Flank
(c) 1995
To see a photo of Lucy (A. afarensis)
The evolutionary transition that is, from the creationist point of view, the most important of all is the evolutionary appearence of human beings. Morris says, "The question of origins becomes most critical of all as it deals with the problem of the origin of man. Is man merely the product of a naturalistic evolutionary process or is he a special creation, prepared by the Creator to exercise dominion over the entire creation?" (Morris, Scientific Creationism, 1974, p. 171) As Strahler puts it, "This gap is the last line of defense for the creationists; it is the moat that surrounds the creationist castle. Nothing means more to them than the belief that God created the human in His own image." (Strahler, 1987, p. 479)
Humans are classified, zoologically, as Homo sapiens sapiens, a member of the primate family of mammals. Although the fossil record of early human evolution is very spotty, enough hominid material has been recovered to form at least a rough outline. According to the latest findings of paleoanthropologists, the immediate evolutionary predecessors of Homo sapiens are known as Homo erectus, whose skeletal remains have been found on several continents and are known by several different popular names such as "Java Man" and "Peking Man". Although Homo erectus walked upright like humans, used fire, and made crude stone tools, its brain capacity was somewhat smaller than that of a modern human, and it had much more primitive features in the face, such as heavy brow ridges and a receding chin.
It is generally believed that Homo erectus itself developed from Homo habilis, an upright form with even more primitive facial features and a still smaller brain size. Homo habilis was apparently the first tool maker, and thousands of crudely chipped lava cobbles have been found near its remains. Because Homo habilis was a toolmaker, it is generally considered to be the first of the true human family, and is the earliest species to be classified as Homo, or in the same genus as modern humans.
The earliest members of the human lineage are classified in the genus Australopithecus. Several species of Australopithecines have been found, and it is generally believed that a number of them are evolutionary offshoots, away from the human line, that specialized in a diet of tough vegetation and died out approximately one million years ago. Two species of the Australopithecines, however, are believed to lie in the direct human line. The most recent of these is Australopithecus africanus, which most paleoanthropologists consider to be the evolutionary ancestor of Homo habilis. (This interpretation is disputed by some authorities, who argue that H. habilis derived directly from the earlier Australopithecines. On the other hand, some authorities do not consider Homo habilis to be a valid species, and lump it together with A. africanus.)
The earliest hominid to be widely studied is Australopithecus afarensis, best-known from a nearly complete skeleton found in Ethiopia in 1974, known popularly as "Lucy". The exact relationship of all these species is still a matter of some dispute, but most authorities have concluded that the "Lucy" type of Australopithecines were ancestral to both the africanus variety and to the evolutionary offshoots. Nearly all authorities agree that Australopithecus afarensis was the earliest member of the upright-walking line that led, some four millions years later, to modern humans. And, as we will now see, the "Lucy" hominids shared a mixture of characteristics which puts them squarely in the gap between primates and humans.
A widespread misconception must be corrected here. It has become almost an axiom among non-paleontologists that "humans are descended from the apes". This in fact is not strictly true, although the creationists do their best to pander to this popular misconception. The hominids are not descended from any of the existing monkeys or apes. Rather, paleoanthropologists have concluded that, approximately 5 million years ago, the human line and the ape line shared a common ancestor, from which the apes went on their separate way, leading to modern gorillas, chimps and orang-utans, and the hominid line went on in another direction, producing the bigger-brained Australopithecines and ultimately you and me. The modern apes are therefore our evolutionary relatives, not our ancestors; we are no more descended from monkeys or apes than you are descended from your sister or cousin.
It would not be inaccurate to characterize the Australopithecus afarensis fossils as representing a primitive apelike head perched atop a humanlike body. At approximately four feet tall, the Australopithecines were much smaller than their evolutionary descendents (male A. afarensis were much larger than females, a characteristic they share with most modern apes but not with modern humans). The skull was relatively small, and the brain was about the same size as a chimpanzee's. The skull presented many features that distinguish apes, including heavy brow ridges and a receeding chin. The teeth on the upper jaw were shaped into a narrow U-shape, with the sides of each tooth row being almost parallel to each other, just as in apes. There was also a noticeable gap in the tooth row to accomodate the long canines, known as the diastema, which is also a trait exhibited by apes but not humans. The A. afarensis canine teeth have large deep roots which cause a noticeable bulge in the jawbone, as in apes--but on the other hand, the crowns of the teeth were small like those of humans.
Lucy's arms were intermediate between those of humans and apes. The upper arm bone, or humerus, was slightly longer, proportionately, than a human's, but not as long as an ape's. The fingers were a bit longer and were slightly more curved than a human's, but not as much as an ape's would be.
In contrast to the apelike features of the head and arms, however, the lower limbs of Australopithecus afarensis were non-apelike, and are virtually indistinguishable from those of humans. In humans, for instance, the heel bones have an enlarged pad composed of spongy bone which absorbs the shock generated by our bipedal mode of walking. Apes, which do not walk on two legs but instead 'knuckle-walk", do not have such a bony pad, but the heel bones of the Lucy skeleton exhibit the same spongy bone. Although Lucy's femur was slightly longer, proportionately, than in humans, it exhibited a number of clearly human characteristics. In humans, the neck of the femur, where it fits into the hip socket, has a thick spongy center as a cushion to absorb the impact of walking, and has a thicker layer of harder bone at the top portion of the joint to withstand the stress. In apes, however, the arrangement is entirely different; the neck of the femur is almost completely solid, with just a small central core of spongy bone. Ape femurs also have a large keel running along the top of the neck where it joins the hip socket. The Australopithecus afarensis femur is identical to the human arrangement.
In apes, the knee joint forms a straight vertical line from the thigh bone through the knee and on into the shin bones. In humans, however, with their upright mode of locomotion, the center of gravity must be shifted inside the pelvic girdle, and this is done by bringing the knees together so they lie directly under the pelvis. Thus, the thigh bone in a human approaches the knee joint from an outside angle, and the limbs do not have the straight-line configuration seen in the apes. And once again, the Lucy type of Australopithecine demonstrates a humanlike type of structure rather than an apelike one. A. afarensis limbs meet at a sharp angle between the lower end of the femur and the knee joint, just as in humans.
It is in the pelvic girdle, however, that the humanlike characteristics of Australopithecus afarensis are most readily apparent. In humans, the pelvic girdle is wide and flattened into a shallow dish shape to hold the weight of the upper body during walking. In apes, by contrast, the knuckles bear most of the weight during walking, and the pelvis is long and narrow. In Lucy, the pelvis was almost identical to that of a human. The only difference appeared in the bones of the sacrum, at the rear of the pelvis. In apes, the sacrum is narrow. In humans, the sacrum must be wide enough to set the hip joints apart for walking. The Australopithecus afarensis sacrum was not only wide like a humans rather than narrow like an ape's, but was actually proportionately wider than that of modern humans. It would be impossible for modern people to have a sacrum as proportionately wide as Lucy's, since this would in turn narrow the opening of the birth canal. In humans, the birth canal must be as wide as possible to allow the relatively large-headed human baby to pass through, but in A. afarensis, with its smaller head and brain, this was not a problem. The Australopithecus afarensis pelvic girdle, therefore, was actually better suited for bipedal walking than is our own.
Confirmation that the early Australopithecines were efficient bipedal walkers came when Mary Leaky discovered a set of hominid footprints pressed into a layer of wet volcanic ash some three and a half million years ago near Laetoli in Africa. Three individual bipeds left their prints, apparently a male, a female and a juvenile. The outlines of their footprints, sharply preserved in the hardened ash, clearly showed that the animal that left these prints was an efficient bipedal walker, like a human--there was not a trace of a divergent big toe such as found in apes, and a very humanlike arch was present. A composite A. afarensis foot, assembled from recovered fossil bones, fits the Laetoli footprints exactly.
Thus, although the experts disagree on details, the basic sequence of human evolution is plain. The hominid line began with little upright-walking Australopithecus afarensis, with its primitive-looking apelike head and small brain perched atop a body that is scarcely distinguishable from that of a modern long-distance runner. From that point on, the basic body plan was set, and nearly all further evolution in the human line took place solely from the neck up. While some of Lucy's evolutionary descendents went off on an ultimate dead end, becoming more and more specialized as vegetation-eaters, one line of descendents demonstrates an ever-increasing brain capacity, accompanied by changes in the teeth and facial structure, which led steadily to Australopithecus africanus, Homo habilis, Homo erectus and finally, about 200,000 years ago, anatomically modern humans. While Lucy was not the last common ancestor between apes and humans (a newly-discovered earlier species tentatively called Arapithecus ramidus appears to be the last common ancestor), she and her species were a transitional from the apelike arboreal primates to the modern upright-walking humans.
To creationists, of course, such a conclusion is not only wrong, but heretical. Creationist religious conceptions of the creation of humans leave them with no choice but to assert, "Although highly imaginative 'transitional forms' between man and apelike creatures have been reconstructed by evolutionists based on very fragmentary evidence, the fossil record actually documents the separate origin of primates in general, monkeys, apes and men." (ICR Impact, "Summary of Scientific Evidence for Creation", May/June 1981)
The fossil record, of course, "documents" no such thing. Typically, the creationists attempt to deny the transitional status of Australopithecus afarensis by denying all of its humanlike characteristics. Lucy, they say, was "just an ape":
"Creationists, on the other hand, insist that these are fossils either of apes or men, not of animals intermediate between apes and men." (Morris, Scientific Creationism, 1974, p. 171)
"Lucy is simply an extinct ape with no clear connection to humans." (Ray Bohlin, "Human Fossils; 'Just So' Stories of Apes and Humans, Probe Ministries, Richardson, Texas, 1994)
"Obviously it too was simply an 'ape'." (Watchtower Bible and Tract Society, 1985, p. 94)
The major thrust of the creationist attack on Lucy comes, surprisingly, on the best-established characteristic of the Australopithecines--their mode of locomotion. Creationist M. Bowden flatly asserts that Lucy "did not walk upright". (Weinberg, 1984, p. 20) Concerning the Australopithecine knee joints which have been found in Ethiopia and elsewhere, he says, "I could find no evidence in print which proves that this knee joint exhibited bipedalism." (Weinberg, 1984, p. 20) Apparently Bowden is incapable of realizing that Lucy's knee joint is identical in every way (except size) with yours and mine. No quadrupedal animal on earth exhibits a knee joint remotely akin to Lucy's. In fact, only one family on earth possesses a knee structure that is similar to Australopithecus afarensis--hominids.
The ICR also attempts to build a case that Lucy could not walk in a humanlike manner and was therefore just an ape. "Australopithecus, in the view of some leading evolutionists," the ICR asserts, "was not intermediate between apes and men and did not walk upright." (ICR Impact, "Summary of Scientific Evidence for Creation", May/June 1981) That the ICR does not name these "leading evolutionists" is not surprising, since no paleoanthropologist of any experience denies that Lucy was as fully bipedal and capable of upright walking as are you and I.
Gish, in his book Evolution? The Fossils Say No!, does not mention Lucy specifically, but says of the Australopithecines in general, "Some fragments of the pelvis, limb and foot bones of these animals have been recovered and, based on studies of these fragments, it has been the consensus among evolutionists that the Australopithecines walked habitually upright . . . In more recent years, however, this view has been challenged . . ." (Gish, 1978, p. 109)
This is simply not true. The Australopithecine fossils are not "fragments", but consist of several nearly complete skeletons, including Lucy. These fossils clearly and convincingly show that Lucy had an erect gait, more efficient in some ways than our own.
The latest criticism of Lucy's gait comes from creationist Ray Bohlin, who states, "If Lucy walked upright, it was distinct from apes and humans. Not exactly what you would expect from a transitional form." (Bohlin, "Human Fossils; 'Just So' Stories of Apes and Humans", Probe Ministries, Richardson, Texas, 1994) I must confess that Bohlin's logic escapes me. Lucy possessed a primitive small-brained apelike head atop a bipedal body that is nearly indistinguishable from that of modern humans. If that is not "exactly what you would expect from a transitional", then I am at a loss to know what Bohlin WOULD expect in such a transitional.
Evolution? The fossils emphatically say Yes!
