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

Wallace Neslund (
Wed, 03 Jul 1996 21:05:16 -0700

Gerrit Hanenburg wrote:
> Paul Crowley <> wrote:
> >> > For example: Did early (bipedal) hominid females carry their infants
> >> > in the ventral position or in their arms or did they (like h.s.s.)
> >> > mostly leave them down in a safe place?
> >>
> >> Such ancient behavior is untestable, and therefore will forever be
> >> unresolved, because it lacks both real evidence and unambiguous evidence.
> >On the basis of our observation of the behaviour of bipedal hominid
> >females (i.e. h.s.s.) we could estimate probabilities; let's say
> >ventral position=5% carrying in arms=10% putting down=85%
> And here you are assuming that modern humans are an accurate
> behavioral model for early hominids,which they probably aren't since
> early hominids were still very apelike in certain anatomical
> characters.Choose the wrong model and you will get the wrong
> estimates.
> Taking a bipedal chimp as a model you might get something like:
> ventral position=70% dorsal position=20% carrying in arms=5%
> putting down=5%.(just off the top of my head)
> Gerrit.

I take it you mean by ventral/dorsal that the infant is holding on by
itself, while carrying in arms means the mother is activly carrying the
infant. I also take it that by infant you mean a very young chimp, i.e.
less than several months old. A baby chimp can grasp its mother's chest
hair and hold on by itself in only a few days time. This was readily
pointed out in the movie "People of the Forest" that studied a chimp.
"family" for several years. If we assume that early hominids were as
hairy as the present day chimps, then chimp. carrying practices would be
a good model for early homids.

If, OTOH, early hominids were as hairless (and by hairless, I mean
absence of long thick chest hair in females,lets not go counting hair
follicles) as present day Hss, then the chimps are not a good model. If
the infant can't hold on to the mothers chest hair, then the mother must
hold on to the infant until it can walk on its own. In present day Hss,
that's well over a year in the best of cases. This means that the mother
would be carying the infant around in her arm(s) for well over a year. In
Hs, and probably any Homo, this year is the period that the infant shows
the most brain growth in a very soft disjointed skull. Since only Homo
has the large brain, rapid skull growth, and extended period of near
absolute helplessness, this might leave "some" trace in anatomy.

Which brings me to the speculation I set out to make. There is a part of
Hss anatomy that is different from the chimps and may directly relate to
infant carrying, and that is the female breast. In chimps, gorillas,
monkeys, and most all other primates the breasts are almost non-existant.
Evan a nursing mother chimp. only has enlarged nipples and very little
breast development. The amount of milk produced, though, seems in no way
insufficient for the infants growth. Hss female breasts are much larger,
even when the female has never had any children. When a female Hss
becomes pregnant, the breasts swell even larger. There should be some
survival value for why Hss females have far larger brests than other

Now comes the speculation. During the first year or so of Hss infant
growth, the infant is helpless. It has a large head and a weak neck,
unable, even, to lift its own head. The mother caries the infant around
in the only usable position, one arm crooked around the infant with its
head against her breast. This leaves the other hand free for eating,
carrying, etc. If Hss had the same hard muscled chest of a chimp. the
infants soft head, wobbling on its weak neck, would be banged against the
mothers chest with every step she took. A constant head beating cannot be
good for rapid and safe brain development. Due to this, Homo females
early on developed a large soft breast to act as a shock absorber to
cushion the head and brain. Children of these mothers were less brain
damaged and therefore more able to survive. In a feed back loop of larger
breasts and better brain growth, Hss females developed the large breast
seen today. Since there was no use for this in males, they continued to
have no breast development. When a positive survival trait is visible, it
also becomes a mate selection criteria. This might explain Hss male
interest in female breast even though they are not sex organs and play no
functional role in procreation. (OK, the last sentence is pure
speculation :) )


God knows, I don't. - Thomas Aquinas

He's some dumb, he not only doesn't know anything,
He doesn't suspect anything. - unknown