Re: Becoming altricial/bi

Paul Crowley (
Tue, 03 Oct 95 01:58:51 GMT

In article <> "J. Moore" writes:

> Pa> The most astonishing aspect of human evolution is not the development
> Pa> of the brain, nor the acquisition of bipedalism. It is that we became
> Pa> "secondarily altricial".
> Pa> This amazing change had one cause: the development of the bipedal foot.

> Our altricial infants -- altricial relative to other hominoids --
> are not the result of bipedal feet, but are clearly the result of
> a change in infant development timing.

> You offer no support for your contention that "the long period was
> already there for physical development". Infants having feet
> adapted for easier and more frequent bipedalism would not depend
> on a period of longer infant development, as you suggest.

You're missing the main point of my posting. I really (at this stage)
have no interest in brain development. I agree that it was mostly much
later (2.5-1.5mya?) but how, why or when, does not concern me now.

My case is that the development of *bipedalism* necessarily involved an
altricial period. The physical development would be that you see in your
own children. They have to learn to walk. But the real thrust of my
case concerns the relationship between the mother and infant. The infant
can no longer cling. It has to be awkwardly carried or put down. This
has a drastic effect on the mother's behaviour. She can no longer
readily flee from predators, or easily forage, or even comfortably sleep.

The altricial period will be long. We might say that it ends when the
hominoid mother would have the same degree of freedom of movement as the
maternal CA. But even a three year old chimp can ride on its mother's
back more easily than a bipedal hominoid of the same age. However,
I am not (at the moment) really concerned how long it was; in any event
it was substantial.

The bipedal hominoid mother could not have spent the altricial period
in the trees. Nevertheless she had to have a safe "home base".

Please respond to these last two sentences.