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

Paul Crowley (
Sun, 14 Jul 96 13:45:26 GMT

In article <> "Gerrit Hanenburg" writes:

> Paul Crowley <> wrote:
> >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 appropriate
> 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)

The phrase "bipedal chimp" is something of an oxymoron; it really
can't be taken for a model. The big difference between bipedal and
quadrupedal hominoids is that, when walking or running, one has a
vertical trunk whereas the other has a horizontal one. This has
drastic consequences. Imagine being a small infant -- Which would
you find it easier to hold onto when your mother is being chased
through the woods by, say, another hominoid?

_ _
_[ }_ ____________[ }
/ || \ / /------------/
/ || \/ Infant //\ XXXX //\
/ || X of bipedal // \ // \
|| X <------ hominoid // // // //
//\ === === === ===
// \ /|\
// // |
// // Infant of quadrupedal hominoid
=== ===

Apologies for the diagram; but I'm trying to emphasise a vital
but usually ignored point. The engineering for bipedalism
entailed radical changes. Whereas both the ventral and the
dorsal positions are feasible for infants of quadrupedal animals,
they are virtually out of the question for bipedal creatures.

It's an important point because once you accept that the ventral
position was impossible for early hominids and that regular carrying
in arms was most unlikely, then altricial infants, home bases,
shared infant caring, a non-woodland habitat -- and much else --
all necessarily follow.