Re: Bipedalism and theorizing... was Re: Morgan and creationists
John Waters (jdwaters@dircon.co.uk)
1 Oct 1996 10:47:37 GMT
Paul Crowley <Paul@crowleyp.demon.co.uk> wrote in article
<843811042snz@crowleyp.demon.co.uk>...
>
> I glad you appreciate the drastic nature of the behaviour
> (although you've overstated it by putting in "new-born" and
> apparently assuming that the infant was left alone).
JW: I'm sorry Paul, I missed the earlier correspondance. Could
you
summarise it for me so that I may know the age of the infant and
its
guardians?
> The point is that this radical change in behaviour
*was_adopted*
> by our ancestors at some stage. Human infants are put down;
JW: Yes, but invariably supervised when in infancy.
>for a long time (several million years) hominid mothers have
not
> been carrying infants close to their bodies, as all their
primate
> ancestors did, and all their primate relatives still do.
JW: I'm not sure I fully understand this sentence. Do mean that
hominid mothers carried their infants with outstretched arms? Or
is
a reference to infants walking by themselves? Sorry to be so
dumb.
>
>
> As you have emphasised, early hominids would be highly social.
> The sharing of infant care would have been the major barrier,
> but if the niche made it essential, then it would have
happened.
> H.s.s. mothers have no great problems about it. When did they
> acquire this characteristic - unique among the primates ?
JW: The sharing of infant care is not unique to H.s.s. In some
species
of monkeys, it is the male who looks after the infants.
> > JW: An extension of the period of helplessness would not
come
> > about simply through infantile inactivity.
>
> Why not? The more active infants would eliminate themselves
and
> leave no descendants. There's no mechanism more effective
than
> that.
>
> Paul.
>
JW: The infantile helplessness of a human baby is not due to
laziness.
It is because the part of the baby's brain which controls its
limbs is not
developed at birth. Prolonged inactivity would simply lead to
the
degeneration of the nerves, leaving the infant totally
incapacitated
-- for ever. (Think of Faben and his paralysed arm.)
This doesn't happen with human babies because the parts of their
physiology which are associated with the undeveloped brain, are
all equally undeveloped at birth. As the brain completes its
foetal
stage after birth, its post foetal development is matched by
synchronous development of the spinal cord, somatic nervous
system, muscles, ligaments and bones. As a result, when the
brain
becomes fully operational, the baby's limbs are capable of
responding
to all instructions from the brain.
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