Male Brains slightly larger than Female Brains [but not proportionately]

R. McPherson rjmcpher at rigel.oac.uci.edu
Sun Aug 3 22:57:49 EST 1997


:
:Howard wrote:
:	First of all, the brains of men and women are comparable when you
:consider the  body size to brain size ratio. This is a well known fact
:of paleoneurology. Secondly, testosterone is Not the only anabolic
:steroid in the human body and there may well be an analogous effect
:from another steroid or even a peptide (such as GH ) in the female.
:
:	BTW, are you aware that testosterone is metabolized to estrogen BEFORE
:it reaches the nuclei of target cells? Surely that throws a monkey
:wrench into the simple reductionist model you propose for male
:superiority.

Exactly correct.  Testosterone and estrogen are interconvertible in brain and
either hormone functions in multiple nuclei both during development and adult
function.  The body size to brain ratio comment is also true but more
importantly, as H. Jerison pointed out years ago (this brain size observation is
much older than the current hype) the amount of cortex between men and women is
comparable.  Thus men and women have about the same amount of cerebral cortical
surface area.  Jerison says that the women have increased invagination so that
more cortex is folded into a smaller cranium. 

So meaningful differences between the brains of men and women (outside of the
sexually dimorphic nuclei of the medial preoptic hypothalamus) remain
undiscovered.

rjmcpher at uci.edu      Ron McPherson





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