Natural Science Forum / Biology / Paleontology / November 2004

With respect to Archimedes Plutunium's recent posts, it should be
noted that Bramble and Lieberman (2004, Nature 432: 345-352) make the
following statements: "Judged by several criteria, humans perform
remarkably well at endurance running, thanks to a diverse array of
features, many of which leave traces in the skeleton. The fossil
evidence of these features suggests that endurance running is a
derived capability of the genus Homo, originating about 2 million
years ago, and may have been instrumental in the evolution of the
human body form."

As far as I understand it, AP's stone-throwing theory proposes that
the modern human capacity for accurate overarm throwing originated in
a common ancestor of Oreopithecus and Orrorin (and hence, presumably,
of all australopithecines as well as Homo spp.). Such an ancestor
lived no later than 7-9 million years ago (late Miocene; see e.g.
Kohler & Moya-Sola 1997,
http://www.pnas.org/cgi/content/full/94/21/11747).

The two hypotheses attempt to explain two entirely separate stages of
human evolution occurring millions of years apart. Criticism of either
hypothesis, on the grounds that it does not explain the same
observations as the other, is therefore entirely illogical.

They may, of course, be rivals for attention or 'status' in their role
as memes, which compete for space in our minds and on the tips of our
tongues rather than over the explanation of facts. It's quite
understandable for a proponent of one to show some impatience and
rhetorically attack another theory in order to divert attention to his
own, but it ain't science. (Personal attacks would be even worse, but
obviously a common enough occurrence in actual, as opposed to ideal,
scientific debate).

But anyway, thanks to AP for inciting a Google search on Oreopithecus
which I hadn't seen much about before (though I'd seen bits an' pieces
of it in a poky little museum in Florence). In a review of a 1997 book
on Miocene apes, H. McHenry wrote "The placement of Oreopithecus had
been hotly debated for decades, but in this book there is remarkable
agreement among the different authors. T. Harrison and L. Rook address
this issue most thoroughly and find overwhelming evidence in its
postcrania of a close relationship to the living great apes and
Dryopithecus". As shown by Kohler and Moya-Sola (PNAS 1997, link
above), the shape of the lumbar vertebrae is Homo-like, different from
other primates, and implies curvature of the spine as in bipedal us;
but the feet are derived in a completely opposite manner, with an
enormous gap and divergence between the big toe and the others. This
has been compared to a bird foot, and would have been quite good for
standing bipedally (as well as gripping branches or trunks, like the
chimp or indriid lemur foot which have independently evolved long and
divergent first toes for climbing), but useless for walking or running
in a human manner. The highly derived foot structure makes it unlikely
that Oreopithecus is ancestral to anything with a 'straight' foot like
ours or Gorilla's.

Here's cheers to all palaeoanthropologists, primatologists and
polymaths.