Re: Obstetrical Crisis

loopy (
11 May 1995 03:45:24 GMT

In article <3ob23m$>, ([Stephanie
Fishkin) wrote:

> I understand (Helen?) Fisher has argued that in our
> evolutionary history there was an obstetrical crisis
> (narrowing birth canal + increasing brain size = lots of
> maternal morbidity). Is there anyone else who supports/
> aruges for this perspective? Is there any evidence that in
> our evolutionary history there was a period of time in which
> the sex ratio was greatly imbalanced towards men, that women
> were dying at greater rates at younger ages? Also, who has
> argued against this proposition and why?

I think you will find lots of support for the "obstetrical crisis" idea. I
guess I'm in that camp myself. Let me suggest some readings --
unfortunately I don't know the exact titles on all of these.

Yearbook of Physical Anthropology (1992) - an excellent paper by L.
Rosenberg on the evolution of childbirth. Gives a graphic comparison of
head size/pelvic inlet size for many different primates.

Am. J. Physical Anthropology (1991) 80:39-71 Tague, R.G. "Variation in
pelvic size between males and females." argues that pelvic size is _not_ a

AJPA Suppl. 18:175 (1994) "Evolution of the pelvis in Homo". Suggests a
change in the birth mechanism.

Walker, A., and Ruff, C. "Reconstruction of the Pelvis". In Walker, A. and
Leakey, R.E., eds. (1993). _The Nariokotome Homo Erectus Skeleton_. They
suggest that pelvic size _was_ a constraint on infant head size.

Also, a recent issue of _Science_ (end of March, I think) has a report on
the AAPA meetings in Oakland. One of the big stories was that a grad
student took x-rays of monkeys giving birth. She found that baboon and
rhesus monkey fetuses rotate during birth, so it may not be a human

One more thing to check out: the book _Heterochrony_ by McKinney and
McNamara. I'm not positive but I think the chaper on human heterochrony
suggests that all humans infants are actually born premature (compared to
animals of comparable size) due to the large head size. This explains the
helplessness of human infants.

Good luck with your research. I think this is a really neat topic.

Lucie Melahn