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'Lucy' walked upright just like us

Wed. July 27, 2005

A robotics model of Australopithecus afarensis locomotion

Dr. William I. Sellers a "computational primatologist" of Loughborough University in the UK, and colleagues under leadership of Professor Robin Crompton of the University of Liverpool, have attempted to settle the question whether `Lucy' was fully bipedal (walked fully upright with a striding gait), as we modern humans do, a question that anthropologists still disagree on.

`Lucy' is the name given to the ~3.2 million-year ago Australopithecus afarensis 40% complete fossil skeleton discovered at Hadar in Ethiopia by Donald Johanson in 1974. This fossil, together with the ~3.5 mya Laetoli footprints preserved in volcanic ash that were discovered in Tanzania in 1978, and presumed to be made by an A. afarensis, were the earliest evidence of full bipedality in a presumed human ancestor.

As they reported in the journal Royal Society Interface, Sellers and colleagues built a robotics model, with assumed virtual muscles for `Lucy', that used genetic algorithms to determined the optimum locomotion for a particular set of body proportions. The resulting model of A. afarensis locomotion closely matched that of the Laetoli footprints. The researchers concluded, "Assuming that the early human relative A. afarensis was the maker of the Laetoli footprint, our study suggests that, by 3.5 million years ago, some, at least, of our early relatives, despite small stature, could sustain efficient bipedal walking at absolute speeds within the range shown by modern humans."

Bipedality too early!: A problem of evolution

This study further confirms what has been a a long-standing problem of evolution, that Lucy's bipedality is too early for Darwinian evolution. The ABC article touches on this: "By suggesting that our ancestors walked upright before the earliest stone tools were made and before brains got bigger, the prediction conflicts with the previous hypothesis that A. afarensis shuffled like chimps walking upright." The original Darwinian gradualistic explanation was that hominid bipedalism was an adaptation to living and hunting on the savannah grasslands that opened up in Africa with the drying of the climate at the Pliocene-Pleistocene boundary about 5 million years ago. However, this "Darwinian package of bipedalism, tool making, and intelligence marching in evolutionary concert is not correct" because Lucy showed that bipedalism occurred well before "the great plains and the immense herds on them [that] are relatively recent aspects of the African environment" (Leakey & Lewin, pp.84-85). The problem for evolution is that:

"The evolutionary shift from quadrupedalism to bipedalism would have required an extensive remodeling of the ape's bone and muscle architecture and of the overall proportion in the lower half of the body. Mechanisms of gait are different, mechanics of balance are different, functions of major muscles are different-an entire functional complex had to be transformed for efficient bipedalism to be possible." (Leakey & Lewin, 1993, pp.83-84).
However, it gets even worse for evolution, with recently discovered hominid fossils that appear to be bipedal, three million years before Lucy, as no less than Dawkins acknowledges:
"WHATEVER THE REASON for the evolution of bipedality, recent fossil discoveries seem to indicate that hominids were already bipedal at a date which is pushing disconcertingly close to Rendezvous 1, the fork between ourselves and chimpanzees (disconcerting because it seems to leave little time for bipedality to evolve). In the year 2000, a French team led by Brigitte Senut and Martin Pickford announced a new fossil from the Tugen Hills, east of Lake Victoria in Kenya. Dubbed `Millennium Man; dated at 6 million years and given yet another new generic name, Orrorin tugenensis was also, according to its discoverers, bipedal. Indeed, they claim that the top of its femur, near the hip joint, was more human-like than that of Australopithecus. This evidence, supplemented by fragments of skull bones, suggested to Senut and Pickford that orrorins are ancestral to later hominids and that Lucy's are not. These French workers go further and suggest that Ardipithecus might be ancestral to modern chimpanzees rather than to us. Clearly we need more fossils to settle these arguments. Other scientists are sceptical of these French claims, and some doubt that there is enough evidence to show whether Orrorin was or was not bipedal. If it was, since 6 million years is approximately the time of the split from chimpanzees according to molecular evidence, this raises difficult questions about the speed with which bipedality must have arisen. If a bipedal Orrorin pushes back alarmingly close to Rendezvous 1, a newly discovered skull from Chad in southern Sahara, found by another French team led by Michel Brunet, is even more disturbing to accepted ideas. This is partly because it is so old, and partly because the site is far to the west of the Rift Valley (as we shall see, many authorities had thought early hominid evolution confined to the east of the Rift). Nicknamed Toumai (Hope of Life in the local Goran language) its official name is Sahelanthropus tchadensis after the Sahel region of the Sahara in Chad where it was found. ... If their discoverers are right that Orrorin and Toumai were bipedal, this poses problems to any tidy view of human origins. The naive expectation is that evolutionary change spreads itself uniformly to fill the time available for it. If 6 million years elapsed between Rendezvous 1 and modern Homo sapiens, the quantity of change ought to be spun out, pro rata one might naively think, through the 6 million years. But Orrorin and Toumai both lived very close to the date identified from molecular evidence as that of Concestor 1, the split between our line and that of chimpanzees." (Dawkins, 2004, pp.94-96).
Note Dawkins' words: "disconcerting," "alarmingly," "disturbing", "problems"! To resolve the problem, Dawkins considers several possibilities, including:
"An extremely rapid burst of evolution occurred immediately after Concestor 1, which itself walked on all fours like a chimpanzee. The more humanoid Toumai and Orrorin evolved their bipedality so swiftly after Concestor 1 that the separation in dates cannot easily be resolved. ... We shall learn from the Galapagos Finch's Tale and the Lungfish's Tale that evolution can be extremely rapid or can be extremely slow. So [this] ... is not implausible." Dawkins, 2004, p.97).
However, Dawkins forgets what he once wrote:
"To 'tame' chance means to break down the very improbable into less improbable small components arranged in series. No matter how improbable it is that an X could have arisen from a Y in a single step, it is always possible to conceive of a series of infinitesimally graded intermediates between them. However improbable a large-scale change may be, smaller changes are less improbable. And provided we postulate a sufficiently large series of sufficiently finely graded intermediates, we shall be able to derive anything from anything else, without invoking astronomical improbabilities. We are allowed to do this only if there has been sufficient time to fit all the intermediates in. And also only if there is a mechanism for guiding each step in some particular direction, otherwise the sequence of steps will career off in an endless random walk. It is the contention of the Darwinian world-view that both these provisos are met, and that slow, gradual, cumulative natural selection is the ultimate explanation for our existence. If there are versions of the evolution theory that deny slow gradualism, and deny the central role of natural selection, they may be true in particular cases. But they cannot be the whole truth, for they deny the very heart of the evolution theory, which gives it the power to dissolve astronomical improbabilities and explain prodigies of apparent miracle." (Dawkins, 1986, pp.317-318. My emphasis)
So Dawkins, like Darwin, when it comes to the crunch, is prepared to abandon natural selection, in order to save "evolution." That is, for Dawkins, like Darwin (who abandoned slow gradualism in the last edition of his Origin of Species, to accommodate the physicist Lord Kelvin's ~100 million-year estimate of the age of the Earth - Darwin, 1872, p.315):
"Darwinism, therefore, began as a theory that evolution could be explained by natural selection. It ended as a theory that evolution could be explained just as you would like it to be explained." (Darlington, 1959, p.60)!


"UK Robotics show Lucy walked upright," BBC, 20 July, 2005.

Darlington, C.D., "The Origin of Darwinism," Scientific American, Vol. 201, May 1959, p.60.

Darwin, C.R., "The Origin of Species by Means of Natural Selection," [1872], Everyman's Library, J.M. Dent & Sons: London, 6th Edition, 1928, reprint.

Dawkins, R., "The Ancestor's Tale: A Pilgrimage to the Dawn of Evolution," Houghton Mifflin Co: Boston MA, 2004.

Dawkins, R., "The Blind Watchmaker," [1986], Penguin: London, 1991, reprint.

Jurmain, R., Kilgore, L., Trevathan, W.R. & Nelson, H., "Essentials of Physical Anthropology," Wadsworth/Thomson: Belmont CA, Fifth edition, 2004, pp.194-199.

Leakey, R. & Lewin, R., "Origins Reconsidered: In Search of What Makes Us Human," [1992], Abacus: London, 1993, reprint.

Lorenzi, R. "'Lucy' walked upright just like us," ABC/Discovery News, 25 July 2005.

Sellers,W.I., et al., "Stride lengths, speed and energy costs in walking of Australopithecus afarensis: using evolutionary robotics to predict locomotion of early human ancestors," Journal of The Royal Society Interface, 18 July, 2005.

I have included the above quotes in my "Problems of Evolution" book outline, PE 14.1.2 "Man ... Uniqueness ... Bipedalism," as notes for when I come to that part of the book itself.

Stephen E. Jones, BSc (Biol)
"Problems of Evolution"