Re: Bipedalism and theorizing... was Re: Morgan and creationists

Paul Crowley (
Tue, 16 Jul 96 13:21:38 GMT

In article <> "Gerrit Hanenburg" writes:

> Chimps,orangutans and gibbons frequently engage in orthograde
> positional behavior,keeping their bodies in a vertical position.The
> infants do not seem to have more trouble holding on to their mothers
> in these situations.

We need to focus on the predominant locomotory behaviour; for
chimps and early hominids that's on the ground. Since orangs and
gibbons hardly ever come to the ground, their locomotory behaviour
is largely irrelevant. In any case, the predominant locomotory
behaviour for female orangs appears to be a slow movement through
the canopy; and that of gibbons is brachiation with raised hind
limbs which help to prevent infants falling off.

> If they can hang on in these situations then there is no reason why
> they shouldn't be able to hang on to the vertical body of a
> facultative or habitually bipedal hairy mother.

Chimps are the only appropriate alternative model. They need
rapid and effective terrestrial locomotion (like early hominids?);
they achieve it with their trunks in a horizontal position.

> >It's an important point because once you accept that the ventral
> >position was impossible for early hominids and that regular carrying
> >in arms was most unlikely, then altricial infants, home bases,
> >shared infant caring, a non-woodland habitat -- and much else --
> >all necessarily follow.

> But you assume that early hominids were fulltime bipeds.This was
> probably not the case.

> Early hominids do not show the fully developed suite of characters
> that are associated with fulltime bipedalism in modern humans

They may not have been built for long distance walking, but they
were unambiguously bipedal. There is no doubt about their only
form of terrestrial locomotion or about the vertical orientation
of the female trunk during it.

> given their small brainsize,didn't yet have secondarily altricial
> infants.

The link between brainsize and secondary altriciality is an
assumption, made without evidence. It's a hang-over from the
days of "brains before bipedalism". It made good sense -- then!