[Neuroscience] How Homosexual Orientation May Form

James Michael Howard jmhoward at anthropogeny.com
Mon Aug 7 15:12:07 EST 2006

Here is my explanation of how homosexual orientation forms.  I have placed
it at my website.

How Homosexual Orientation may Form

(Copyright 2006, James Michael Howard, Fayetteville, Arkansas, U.S.A.)

I define sexuality as activation of neuroanatomic, physiological circuits
in the brain that stimulate sexual activity in response to environmental
cues and activity from pleasure circuits in the brain.  (I think hunger,
etc., work the same way.)  I think sexual orientation is affected by growth
and development of neuronal nuclei in the brain
These centers may be affected by molecules from the environment (smells or
pheromones).  If one has smaller sized nuclei, the amount of molecules
required to activate the nuclei may be less.  That is, fewer cells, or less
growth of cells, in a group may be activated by fewer molecules to "send" a
signal for behavior.  I think growth and development of some of these
centers is similar in women and homosexual men; I think research has
demonstrated similarity in size.  Therefore, these centers may be activated
more rapidly than larger centers because of less surface size and
therefore, the receptor density to nuclei size is increased.  So, as an
individual grows and develops and is around adults and other children,
girls and homosexual boys will be activated sooner by lower levels of
molecular signals (scents or pheromones).  In this case, the smell of men
may be stronger and affect stimulation of these areas more rapidly,
therefore, orienting these individuals towards responses to males.  That
is, an activating smell may affect smaller nuclei more rapidly and
establish a sexual link with the main activator, men.  Larger nuclei may
require increased activation and these may be activated later because of
increased activation by arrival of young women to puberty.  This may also
explain the strong bonds between males that are later supplanted by women.

There may be support for my hypothesis.  A derivative of both progesterone
and testosterone, 4,16-androstadien-3-one (AND), has been studied as a
"pheromone" in male and female homosexuality. AND activates the brain of
heterosexual women and homosexual men similarly (first reference below) but
not homosexual women (second reference below).  Homosexual women were
activated by "the estrogen-like steroid estra-1,3,5(10),16-tetraen-3-ol
(EST)" which is also thought to be a human pheromone somewhat similarly to
heterosexual men (second reference below).  This differential in activation
may be due to increased activation of smaller nuclei in women and
homosexual men.  Of interest here is that both men and women will produce
AND which will stimulate both hetero- and homosexual orientation depending
upon growth and development of the affected child, in utero.  So, a child
with heterosexual growth and development of their brain nuclei will develop
according to their own program and not be affected by either male or female
homosexual parents.

At puberty, testosterone, in men and women, increases activation of these

"In contrast to heterosexual men, and in congruence with heterosexual
women, homosexual men displayed hypothalamic activation in response to AND.
Maximal activation was observed in the medial preoptic area/anterior
hypothalamus, which, according to animal studies, is highly involved in
sexual behavior." (Proc Natl Acad Sci U S A 2005; 102: 7356-61)

"In contrast to heterosexual women, lesbian women processed AND stimuli by
the olfactory networks and not the anterior hypothalamus. Furthermore, when
smelling EST, they partly shared activation of the anterior hypothalamus
with heterosexual men." (Proc Natl Acad Sci U S A 2006; 103: 8269-74).

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