Re: The Gathering Hypothesis

J. Moore (
Mon, 15 May 95 00:07:00 -0500

RA> I've been enjoying the discussion in this newsgroup, so I thought
RA> I'd toss out this idea as strawman argument. Most professionals
RA> are having a problem explaining human bipedialism in terms of a
RA> environmental adaptation. Maybe it isn't. Could it instead be
RA> the result of sexual selection? Several primate species have
RA> special features caused by sexual competetion. I can easily
RA> see an upright posture used as part of a mating ritual (I'm
RA> taller than my competetion). This could push the trait through
RA> a brief awkward phase and the its other benefits would insure
RA> its further development.

Just a couple of preliminary points: #1 is that you aren't putting forth
a "strawman argument"; a strawman argument is when you (either
inadvertently or deliberately) mischaracterise *someone else's*
argument(s) and then reply to the mischaracterised version but claim
you've replied to the other person's actual argument. This isn't what
you're doing; you're just throwing a idea into the pot. ;-)
Point #2 is that although people so often want to find *a* reason for
something, it's usually *a number* of reasons that should be looked for.
There are undoubtedly a number of reasons habitual bipedalism became the
hominid trademark. Among them are the sorts of things apes use
bipedalism for (displays, carrying, getting food from branches).

Now to your suggestion: it isn't new. Nancy Tanner made this suggestion
in *On Becoming Human* and she made sure to repeat it in every paper and
talk she did after. Let me quote a few lines from pages 163-164
of *On Becoming Human*:

"Sexual selection also increased the contribution of genes from
males who exhibited frequent bipedalism."
"Further, obvious visual cues such as a *bipedal* male's erect
penis could have attracted female attention and action."
"As the female hormonal cycle and ovulation came to contribute less
to timing of her arousal, it is not illogical that visual cue could
become increasingly significant. If so, sexual selection for
bipedalism would be yet another instance of natural and sexual
selection together advancing the species' adaptation farther along
the same path for both females and males."

Also interesting to me has been the reaction of audiences to these
suggestions. She also brought up sexual selection as one possible
aspect contributing to the marked reduction in canine tooth sizes for
males. She suggested that female choice of males with smaller canines
contributed to the reduction in sexual dimorphism in canine teeth
(there's been both overall reduction and reduction in dimorphism). When
Nancy gave talks, she always mentioned this in the senetence immediately
after she mentioned the above female choice for bipedal males. Although
these same scientists seem able to wax ad nauseum about female sexual
characteristics, they always exhibited a stunned silence at the notion
of females liking to see bipedal males' penises. The following idea
about teeth then brought a gasp of relief. Interestingly, until Dean
Falk mentioned the bipedalism part of this in her book *Braindance*, the
only people who weren't shocked were the young female reporter who
reported it in an article in the Santa Cruz paper, and another female
reporter for *Newsweek*. Apparently the general public is not so
shockable as academics are.

Jim Moore (

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