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

Gerrit Hanenburg (
Thu, 11 Jul 1996 08:58:16 GMT

Ralph L Holloway <> wrote:

>Maybe the female breast has multiple
>functions, and that sexual attraction and signalling is one important
>aspect of that total function, with more importance than as any sort of
>augmentation of milk.

I've looked up some species averages for life-history variables.
-neonatal bodyweight:
Homo sapiens-3300.0 g.
Pan troglodytes-1756.0 g.

-neonatal brainweight:
H.sapiens-384.0 g.
P.troglodytes-128.0 g.

Ratio neonatal brainweight/neonatal bodyweight:

In my opinion these differences alone pose a different nutricional
demand in that H.sapiens neonates need a higher daily caloric intake.
This difference becomes even greater if we take into account the fact
that a human infant has a far higher rate of braingrowth in the first
year of life (almost tripling it's brainsize)
Given that the infant subsists almost entirely on mother's milk during
the first year of life,I thought that the caloric output of the human
breast must be greater than in chimpanzees and that one way of solving
the problem would be an increase in the amount of glandular tissue.
This could explain part of the difference in breastsize between humans
and apes.

(Source of neonatal body- and brainweight:Harvey,P.H.,Martin,R.D.and
Clutton-Brock,T.H.(1987),Life Histories in Comparative
Perspective.p.185 in Smuts, al.(1987),Primate
Societies,University of Chicago Press)