Re: Becoming altricial/bipedal
Paul Crowley (Paul@crowleyp.demon.co.uk)
Wed, 04 Oct 95 06:54:58 GMT
In article <44s2ca$gcm@erinews.ericsson.se>
etxlmka@tn.ericsson.se "Lisbeth Andersson" writes:
> Or as an alternative: The earyl hominid baby's development was not
> noticeably different from the development of the baby of the
> common ancestor, which made it possible for the early hominid mother
> to place it on her shoulders, where it could *sit* and cling to the
> mothers hair.
You have a good point. If our ape ancestors had produced more
precocial infants this might well have happened - and we probably
would not be here.
Take a look at pictures of newborn chimps, orangs or gorillas. They are
remarkably helpless (or altricial) by comparison with the offspring of
other mammals such as gazelles. They can do little more than hang on for
the first few months - using all limbs. Primatologists often express
surprise that they don't stay inside for longer, since their mothers have
plenty of room, and have very easy births. Presumably they are little
more trouble outside than in. They are certainly not capable of sitting
on shoulders and holding on in the way you envisage. Nor presumably were
the infants of the first hominids.
To correct a point you made in an earlier posting: Newborn chimps,
orangs, and gorillas have roughly the same head/trunk proportions as
homo sapiens. Newborn h.s infants have much more fat in their bodies.
Presumably early hominid infants would follow the standard ape pattern
and have smaller heads and smaller (thinner) bodies and would be no
more capable of holding on with two arms than would an ape that was
born without feet.
> This is the first time I hear that foot development instead of brain
> deveolopment should cause a long infant stage. All previous sources
> I've seen claims that the helpless infant stage is linked to brain
> development.
Science progresses.
> And since the brain of the earliest found hominids
> seems to be very similar to chimp brains, I see no reason to
> assume that our first bipedal ancestor were altricial.
Proposed experiment: Bind the feet of newborn apes and see what happens.
What would be the survival rate in the wild?
Paul.
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