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

Paul Crowley (
Sat, 14 Sep 96 23:30:27 GMT

In article <01bb90c5$6bdb1ea0$> "John Waters" writes:

> ... my hypothesis that bipedalism was caused
> by the extension in the period of infantile helplessness from
> 24 hours (as in Apes today), to three months (as in Hss today).

> [..] Once the period of infantile helplessness
> extended beyond a week, the nursing female would have been
> forced to adopt a bipedal form of locomotion while carrying
> ^^^^^^ her baby in her arms.

Whenever you see the word "forced" in an evolutionary argument
hackles should rise.

> The evolution of the increase in infantile helplessness is
> not dependent upon an increase in brainsize. It can be due to
> a reduced body size. In cases where a specie needs to develop
> an improved power to weight ratio, this can be achieved through the
> development of a slimmer and slighter body structure.

You're saying (a) proto-hominids got smaller (b) their brains
got relatively larger, (c) this lead to more altricial infants
which (d) caused bipedalism.

I find this, in itself, a bit hard to accept. You're saying that
smaller mothers with more slowly developing infants would have a
significant advantage over larger females with faster developers.
It does not sound right. Smaller size can be an advantage, but
more altricial infants? They'd impose great difficulties on
their mothers at a particularly stressful time. On the face of
it, an infant with an altricial period of one week would have a
much smaller chance of survival than one with a period of a day.
You need to be able to specify some very substantial compensatory