Did Lucy walk upright?
by Michael Oard
For over 20 years, Lucy or Australopithecus afarensis has been considered
one of our first ‘ancestors’, mainly because it supposedly walked upright.1 Donald Johanson, the discoverer
of Lucy near Hadar, Ethiopia, reflects on the significance of walking upright:
‘In 1973, when I was barely out of graduate school, I found a humanlike knee
joint that proved beyond doubt that our ancestors walked erect close to three and
a half million years ago—long before they developed the big brains that had
once been thought to be the hallmark of humanity.’2
Evolutionists place great importance in walking upright and use it to define man’s
ancestors, although the origin of bipedalism is shrouded in mystery:
‘Bipedalism has traditionally been regarded as the fundamental adaptation
that sets hominids apart from other primates. Fossil evidence demonstrates that
by 4.1 million years ago, and perhaps earlier, hominids exhibited adaptations to
bipedal walking. At present, however, the fossil record offers little information
about the origin of bipedalism … .’3
So it is important to know whether some fossil ape-like creature was bipedal or
not.
Regardless of the status of Lucy’s knee joint, new evidence has come forth
that Lucy has the morphology of a knuckle-walker,4 which is a distinctly quadrupedal specialization
characteristic of some living apes and is quite different than walking upright.
Richmond and Strait identify four skeletal features of the distal radius of the
living knuckle-walking apes, chimpanzees and gorillas. They also identify similar
morphological features on two early ‘hominids’, including Lucy:
‘A UPGMA clustering diagram … illustrates the similarity between the
radii of A. anamensis and A. afarensis and those of the knuckle-walking
African apes, indicating that these hominids retain the derived wrist morphology
of knuckle-walkers.’5
In an interview, Richmond stated that after they analyzed the wrist characteristics
of living knuckle-walkers, he and Strait walked across the hall to check plaster
casts at the National Museum of Natural History: ‘I walked over to the cabinet,
pulled out Lucy, and—shazam!—she had the morphology that was classic
for knuckle walkers .’ [emphasis mine]6
This seems like strong evidence that these supposed early ancestors, including Lucy,
actually were knuckle-walkers and hence did not walk upright. But no, the authors
assume that the previous evidence for bipedalism is sound, and that these ancestors
only retain knuckle-walking features from a previous ancestor.
It is true that there are some morphological features for knuckle walking that are
missing in Lucy,6 but these features are not always
present in living knuckle-walkers either, so that researchers cannot rule out that
Lucy was a knuckle-walker.5 The researchers are almost
forced to reject that Lucy was a knuckle-walker, otherwise it would have adaptions
for walking upright, climbing trees (based on the long arms and fingers) and
knuckle walking. This presents an evolutionary difficulty in how Lucy can have
three fairly distinct behavioural characteristics. Furthermore, it makes it difficult
to determine which of these characteristics are related to its lifestyle and which
are no longer functional but are carryovers from its previous ancestry.7
The authors use this new information to settle a fine point in cladistic analysis:
whether knuckle-walking originated independently by parallel evolution
in the chimpanzee and gorilla or was a shared-derived character from the putative
ancestor of humans, chimps and gorillas. Richard and Strait now claim the latter
hypothesis. Molecular DNA comparisons, previously contradictory, now support this
new cladistic analysis.
However, the finding of the knuckle-walking morphology in Lucy has added confusion
to the supposed hominid phylogeny. Lucy was thought to be the ancestor of A. africanus
because Lucy’s skull was more chimpanzee-like, but now the foot bones and
lower leg of a new A. africanus specimen unexpectedly are more apelike
than Lucy.8 A. africanus
also has more apelike limb proportions than Lucy.8
On the other hand A. africanus did not have the knuckle-walking morphology
that Richmond and Strait discovered in Lucy. So it seems that different parts of
the body tell a different evolutionary story:
‘The work by Richmond and Strait further complicates the picture: it suggests
that A. afarensis retained some knuckle-walking features, whereas A. africanus
did not. It is no longer a case of the skull pointing to one set of phylogenetic
relationships, and the postcranial skeleton—everything but the skull—to
another. Rather, different parts of the postcranium may not support the same phylogenetic
hypothesis.’8
Maybe there is no evolutionary relationship at all, and these are all unique, extinct
apes?
One gets the impression that much subjective judgment goes into phylogenies. Reading
between the lines, one also sees the subjective nature of choosing characters in
determining evolutionary relationships. If a similar character cannot be related
by evolution, it is simply assumed to be due to parallel or convergent evolution,
in other words to a hypothetical similar environment.
Related articles
Further reading
References
- Johanson, D.C. and Edey, M.A., Lucy: The Beginnings of Humankind,
Simon and Schuster, New York, 1981. Return to text.
- Johanson, D. and Shreeve, J., Lucy’s Child: The Discovery
of a Human Ancestor, William Morrow and Company, Inc., New York, p. 19, 1989.
Return to text.
- Richmond, B.G. and Strait, D.S., Evidence that humans evolved from
a knuckle-walking ancestor, Nature 404(6776):382, 2000.
Return to text.
- Richmond and Strait, Ref. 3, pp. 382–385. Return
to text.
- Richmond and Strait, Ref. 3, p. 383. Return to text.
- Stokstad, E., Hominid ancestors may have knuckle walked, Science
287(5461):2131, 2000. Return to text.
- Collard, M. and Aiello, L.C., From forelimbs to two legs, Nature
404(6776):340, 2000. Return to text.
- Collard and Aiello, Ref. 7, p. 339. Return to text.
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