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

19 Jul 1996 13:12:47 GMT

Paul Crowley ( wrote:
: 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!

: Paul.

Harry Erwin, Internet:, Web Page:
49 year old PhD student in computational neuroscience ("how bats do it" 8)
and lecturer for CS 211 (data structures and advanced C++)