Re: Bipedalism in Prehominids?

Erin Miller (
12 Apr 1995 17:25:18 -0500

In article <3mfcjl$>,
HARRY R. ERWIN <> wrote:
>TeKnO-RaVe-StOmPeR ( wrote:
>: In a previous article, (HARRY R. ERWIN) wrote:
>: Interesting. Do you think that it is reasonable to assume that
>: sexual dimorphism between early male and female hominids beginning
>: with afarensis is an indication that there was a plolygynous social
>: structure present? Ie: one adult male and several adult females.
>Very definitely. Sexual dimorphism corresponds to harem mating systems.

Certainly doesn't explain the Orangutan, which I believe has the highest
sexual dimorphism ratio. Nor does it explain many macaque species which
have high dimorphism rates with multiple males in the group. There may be
an alpha male, but it is far from a harem situation. As well as the fact
that many groups which are in a harem mating system do not have large
dimorphism ratios.

>: And if so, then what is the implication? Would it be one male
>: protecting and providing meat to the females? And if not, then
>: what is the implication of sexual dimorphism, particularly in the teeth?
>Possibly a chimp or gorilla style system.

Those are two VERY different systems. Possibly either, sure. Possibly a
multitude of other choices as well. Really, you can't say anything based
on the evidence so far. Everything is idle speculation.

>: In (Johanson and Edey, 1981), there is a reference to the discovery
>: of 13 individuals at one Hadar site representing males and females of
>: all ages. Johanson has suggested that they were a family group.
>: If this is so, how would the young have been reared? Would they
>: have clung onto the mothers' fur (assuming fur)? while she
>: scavanged or foraged for food? If there were a signifigant amount
>: of attention paid to the young, then would it be reasonable to
>: extrapolate that backwards to our earliest hominoid ancestor?
>I suspect erectus was the first species to have pair-bonding and extremely
>dependent young (see the publication on the Turkana boy). In chimps, the
>females move and in other species, the males move. If the latter was the
>case, the local group of females would have been related and would
>probably have shared child-rearing responsibilities. If the former, there
>would have been less cooperation.

Gibbons pair bond. In chimps males often leave too. In gorillas both
leave. In gibbons both leave. In orangs both leave. I think this sort of
speculation is the type where somone says "hey, I found something
corresponding in primate behavior so it must be similar," without taking
into account that it may be similar in MANY different forms of primate


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Erin Miller
University of Chicago / Anthropology Department /