Describe some of the biological theories of homosexuality.

While there are no concurrent answers as to why some
individuals develop a homosexual orientation, many researchers believe that biological
factors, among other things, play a significant role in determining a person's sexual
orientation.  To begin with, twin studies have indicated that there is a possible
genetic component to sexual orientation.  Studies have shown that in identical twins
where one identifies as homosexual, there is around a 52% chance that the other twin
will identify as a homosexual as well.  In fraternal twins, the chances decrease to
about 23%.

In neurological studies, researchers have found that the
brain structure is sexually dimorphic, which means that men and women's brains are built
differently.  Some studies have found size differences in certain structures of
homosexual and heterosexual brains, such as the hypothalamus, the suprachiasmatic
nucleus and the anterior commissure.  Other researchers have suggested that differences
in hormone levels, especially during prenatal development, may be associated with a
person's sexual orientation.  The sex hormones, testosterone and estrogen, impact the
fetus's developing brain, and an excess or deficiency in one of these hormones may cause
a disruption in this process.
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