How did we become bipedal?

Cameron Laird (claird@Starbase.NeoSoft.COM)
24 May 1994 17:57:08 -0500

I'm surprised that there's been no mention of

Kingston, John D., Bruno D. Marino, and Andrew Hill
1994 "Isotopic Evidence for Neogene Hominid Paleo-
environments in the Kenya Rift Valley", Science,
volume 264, pages 955-959 (13 May 1994)

I'll take it on myself to say a few words about it, organized
along these lines:
1. NetNews background;
2. a review of the article;
3. tribute to the departed.

Newsgroup chronology
During its fewer-than-five months of existence, the one topic that
has recurred most vigorously in sci.anthropology.paleo has been
the Aquatic Ape Theory, an inheritance that s.a.p assumed at its
birth after two years of discussion in sci.anthropology. In the
local dialect, this often appears under the acronym AAH, where 'H'
stands for "hypothesis", emphasizing the lack of seriousness which
s.a.p seniors accord the claim. In any case, the null hypothesis
goes under such rubrics as SAH or SAT, where 'S' can be taken as
"standard" or "savannah". A few of us object to the latter; I'm
one amateur, for example, who thinks it more likely that we got
to be hominoids while still spending much of our lives in the trees.
That's the background. I'll now select excerpts from Kingston et
al. to summarize the relevance of their article to the concerns
I've seen expressed in these groups:

A review
"Bipedality ... has been regarded as an adaptive response to a
transition from forested to more-open habitats in East Africa
sometime between 12 million and 5 million years ago. . . . Im-
plicit in most of these explanations is that as Middle to Late
Miocene rain forests in Africa became restricted in distribution,
drier and more seasonal woodland and grassland communities became
widespread ..." However, "[a]nalyses of the stable carbon iso-
topic composition ... from the Tugen Hills succession ...
indicate that a heterogeneous environment ... has persisted for
the last 15.5 million years. Open grasslands at no time domi-
nated this portion of the rift valley. . . . If hominids
evolved in East Africa during the Late Miocene, they did so in
an ecologically diverse setting."

Kingston et al. briefly but cogently explain the geography and
especially pedology of western Kenya, the phytophysiology of C3
and C4 metabolism, and a bit of the relevant paleontology. With
appropriate references and three suggestive, if minimal, figures,
they present their results: "While the course of human evolu-
tion was surely affected by environmental change, our data suggest
that interpretations of the origin of hominids in East Africa
should be considered within the context of a heterogeneous mosaic
of enviroments rather than an abrupt replacement of rain forest
by grassland and woodland biomes."

The departed
One poster who argued vehemently for the importance of seeing
humans as inhabitants of margins (riverside; transition from
prairie to forest; and so on) was Gil Hardwick. Mr. Hardwick's
name will probably be preserved on UseNet only as the first
person to lose a lawsuit for damages done by defamatory email.
There was a bit more to him, though, than his vitriolic letters
and articles, and I think it right to recognize that before our
collective memory of him degenerates to include only the worst
of his bile.

I've narrowed follow-ups.


Cameron Laird ( +1 713 267 7966 ( +1 713 996 8546