Re: please send vestiges

Matthew O. Fraser (
Thu, 01 Aug 1996 22:13:15 -0400

In article <4tftcp$>, Cason) wrote:

> I am looking for evolutionary vestiges, or evidence of evolution in
> people. An example would be the Coccyx spine as a modified tail. The
> stuff you send can fall in any category. It can be psychological,
> anotomy, or physiology. Anything you can think of would be facinating
> to me. Thanks...
> --------------->AC

Hey Andy,

Don't know if this is what you are looking for, but my PhD research was on
the Neuroendocrinology of Puberty in Primates. It appears that every male
primate studied to date is born with a fully functional
hypothalamo-pituitary-gonadal axis (sans spermatogenesis). Infant males
have testosterone levels equal to those of adults. This comes from the
active axis, not the mother. Soon after (I'm talking months-year,
depending on the species), the hypothalamic part of the axis shuts off,
and, as it is the engine that drives the axis, the whole thing crashes.
Prior to the onset of puberty, the hypothamic part of the axis
"reawakens" and the adult level of secretion is reestablished within a
short time.

*No other species outside of primates show this pattern.* Instead, they
demonstrate a gradual development of the axis until adulthood.
Testosterone levels rise from shortly after birth continuously to plateau
at adult levels. Same holds true for the pituitary hormones, suggesting
that it's due entirely to the development of the hypothalamic drive. One
can see neuroanatomical correlates to this development as well, at the
level of the median eminance innervation by gonadotropin-releasing hormone

Primates due the everything else bit in utero.

So, in a sense, it's a physiological vestige of being Primate. Not lost,
presumably, from the ancestrial primate pattern.

Hope that's usefull,


Matthew O. Fraser "If you can't answer a man's
Department of Pharmacology arguments, all is not lost.
School of Medicine You may still call him
University of Pittsburgh vile names"
Pittsburgh, PA 15261 John Homans