Cynthia
Chappell, Pflag Houston Voices
“A Biological Explanation for
Human Orientation” DVD
Presented at Reconciling
Hearts Forum November 12, 2006
Cynthia is a Pflag Mom. Her
oldest son came out to their family when he was thirty years old. Seven years later Cynthia, a scientist
herself, has explored the research about homosexuality to inform herself. She found the information to be hard to
access for the general public and so decided to present the information in a
more accessible format. Thus, her lectures and this DVD. In the DVD she attempts to present
1. Fundamental
biological concepts
2. The latest and
best evidence from studies of good scientific design that have been replicated
3. The influence
of such research on human populations
Biological diversity has made
human beings successful. Factors of
height, weight, blood pressure, immune response, etc. are what keep humans
robust. All of these factors follow a
normal distribution which appears as a bell curve on a graph. Sexual orientation is another factor like
these with heterosexuals being the majority and the minority (the tails) being
about 4-5% exclusively gay males and 2-4% exclusively lesbians.
Scientific studies are based
on population-based evidence, on groups rather than on particular
individuals. One case on one person
cannot prove or disprove a generalization.
Associations for characteristics in a population must be statistically
significant. An example is
“smoking.” We know that smoking is
dangerous to your health and causes cancer, but small numbers in the population
don’t get cancer when they smoke and other small numbers get cancer and have
never smoked. The exceptions don’t
disprove the generalization.
It is difficult to set up a
study design without having some deficiencies.
With regard to studies of homosexuality, it is difficult to accurately
define what a “homosexual” is because data is reported by persons who have
different knowledge themselves based on cultural differences and fear of
revealing themselves. The populations are therefore, not “clean”. An example of cultural differences is that in
People question whether
homosexuality is primarily biological or psychosocial. One study helps answer
the question. Thirty-nine genetic males (XY) who were born with poorly
differentiated genitalia were followed until adulthood after they were
surgically reassigned and raised as females.
This means that they received all of the cultural expectations for being
female. As adults they were asked how
they identified sexually; 69% identified as males; 7% as females; and 24%
refused or couldn’t answer. This study
certainly points to a genetic influence.
Many family,
or pedigree studies, tend in the same direction. In families of a gay
person, there are increased rates of homosexuality in maternal male relatives;
5-25% of sisters of lesbians are lesbian; 9-22% of brothers of gays are gay
also, all much higher incidences than in families of straight persons. There is some co-incidence with opposite sex
siblings which is statistically significant as well. Six studies of identical twins show a 52%
likelihood of sharing the same homosexual orientation whereas with fraternal
twins the likelihood is 22%. Gay men
also have more older brothers who are gay, although
there is no association between gay men and older sisters. When the age of the parents is controlled
there are no associations.
Some have asked, “Is there a
gay gene”? There is no one gene
responsible for sexual orientation. There are at least 51 genes responsible for
sexual development with seven showing the greatest effect. However, in linkage
studies (molecular), there is a 66-67% genetic linkage between gay brothers and
58% between lesbian sisters. A brother
of a gay man has a 9-22% chance of being gay, while in the general population
the incidence is 4-5%. A sister of a
lesbian has a 5-25% chance of being lesbian also while in the general
population the incidence is 2-4%. There
is obviously something genetic going on.
Research seems to suggest
that although sex, maleness or femaleness, is established at conception, actual
sex differentiation seems to occur between the 8-16 week of gestation. It appears that fetal hormones present during
that time act on all body tissues giving rise to male or female
characteristics. The presence or absence
of certain androgens can result in either feminization or masculization
of a biologically male or female. For
example, sometimes genetic males are born with feminization of testes and are
often reassigned by physicians to females because their organs look
female. In a study following such cases
93% of these persons expressed attraction to men. Similarly, genetic females with masculization who were surgically altered to male traits
expressed a 70% attraction to females.
Additionally, there have been
brain studies and examination of a multitude of characteristics that show
associations between “gayness” and certain physical characteristics. The upshot
of most current studies is that the genetic component is extremely
significant. If a biological cause is
apparent, it is evident that homosexuality is a normal variant of human sexuality,
about which a person does not have a choice. Nor should the person have to
choose.
With the increased prevalence
of anti-discrimination laws and exposure of variations in sexuality through the
media, openness on the subject of human sexuality seems more possible than it
was just a few years ago. It is clear
that expecting persons to change something about themselves over which they
have no causal control is counterproductive.
(These notes do not communicate all of the essence of the DVD. So the notes are somewhat inadequate. However,
we hope that for those who are interested in “cause” this might help.)