a) Twin Studies
1.
Bailey and Pillard (1991)
o
52% of identical twin brothers were both gay
o
Not 100%
o
Biased applicant pool
2.
Bailey, Dunne and Martin (2000)
o
30% of identical twins were both gay
o
Not replicated
3.
Bearman and Bruckner (2002)
o
6.7% of identical twins were both gay
4.
Långström, Rahman, Carlström, Lichtenstein
(2008)
o
The largest twin study of same-sex sexual
behavior attempted so far – 3,826 twins
o
Male: Genetics 34%-39%, Shared Environment 0%,
Individual-Specific Environment 61%-66%
o
Female: Genetic 18%-19%, Shared Environment
16%-17%, Individual-Specific Environment 64%-66%
o
“Although wide confidence intervals suggest
cautious interpretation, the results are consistent with moderate, primarily
genetic, familial effects, and moderate to large effects of the non-shared
environment (social and biological)
on same-sex sexual behavior.”
o
95% Confidence Interval: Genetic 0%-59%, Shared
Environment 0%-46%, Individual-Specific Environment 41%-85%
o
Only 7/71 pairs of male MZ and 26/214 pairs of
female MZ had same-sex partners – 10% male and 12% females
o
Conclusion – Both environment and biological paly
roles. Identical genes don’t behave identically.
b) Brain Structure
1.
Simon LeVay (1991)
o
The hypothalamus is believed to play a role in
the regulation of sexual behavior in animals.
o
41 cadavers: 19 gay men – all died of AIDS, 16
(presumed) heterosexual men – 6 died of AIDS, 6 (presumed) heterosexual women –
1 died of AIDS
o
Studied neurons group size in hypothalamus,
INAH1, INAH2, INAH3, AND INAH4
o
He found that the INAH3 group of neurons appeared
to be twice as big in (presumed) heterosexual male group as in the gay male
group.
2.
Byne, Tobet, Nattuace, et al. (2001)
o
Could not replicate
3.
LeVay’s Conclusion
o
“It’s important to stress what I didn’t find. I
did not prove that homosexuality is genetic, or find a genetic cause for being
gay. I didn’t show that gay men are born that way, the most common mistake
people make in interpreting my work. Nor did I locate a gay center in the
brain…Since I look at adult brains, we don’t know if the differences I found
were there at birth or if they appeared later.”
C) Chromosomes
1.
Hamer, Hu, Magnuson, Hu, Pattatucci (1993)
o
Studied 76 gay brothers and their families
o
Hamer noted that gay men had more gay relatives
on the maternal side of the family – so the studied X chromosomes of gay men
o
Found that 83% of gay men had similar alleles in
the distal region of Xq28
o
This was popularly (but inaccurately) dubbed the
“gay gene” by media (Time Magazine)
o
Hamer himself (who was gay) clarified
“environmental factors play a role. There is not a single master gene that
makes people gay…I don’t think we will ever be able to predict who will be
gay.”
o
No control group.
2.
Bailey et al. (1999)
o
Could not replicate
3.
McKnight and Malcolm (2000)
o
Could not replicate
Studies on Environment
a) Twin Studies
1.
Långström, et al. (2008) showed a moderate to
large effects of non-shared environmental factors which influenced same-sex
sexual behavior
b) Familial Factors
1.
Jonas (144); West (1959; Bieber et al. (1962);
Brown (1963); Braatan and Darling (1965); Evans (1969); Snortum (1969); Biggio
(1973); Siegelman (1974); Socarides (1978); Bell, Weinberg and Parks (1981);
Millic and Crowne (1986); Nicolosi (1991); Phelan (1993); Seutter and Rovers
(2004)
2.
Kendler, Thornton, Gilman, Kessler (2000)
studied American twins and showed that familial factors influence sexual
orientation
3.
Lung and Shu (2007) studied 275 men in Taiwanese
military and concluded “paternal protection and maternal care were determined
to be the main vulnerability factors in the development of homosexual males.”
c) Childhood gender
non-conformity, Fraternal birth order, Urban vs Rural
Critique of Studies
a) Environment
1.
Confusing correlation with causation
2.
Causation is when one factor or multiple factors
bring about something being studied – cause and effect
3.
Correlation is when ether is some type of
relationship between variables
o
Casual, effectual, indirect, coincidental?
o
Correlation does not mean causation
b) Biology
1.
Biological factors ≠ born gay (innate)
To say that people are born gay is different from saying
what is the cause of being gay.
Born gay is asking a “WHEN” question: When the factor(s)
influences a person.
We have not even figured out the causes/factors, how can we
already jumped to conclusion by saying when?
2.
Nor born gay? What about choice?
3.
No empirical, objective test for homosexuality
There is no
homosexual test like blood test or X-ray. Homosexual is self-declaration
Biblical Anthropology
a) Psa 51:5 – All born with a sinful nature
b) Genetics could influence sin
c) Example: Alcoholism
o
“Genetic factors appear to play a significant
role in alcoholism and may account for about half of the total risk for
alcoholism,” but “other factors usually come into play, including biology,
genetics, culture, and psychology”
d) Biology doesn’t make something morally permissible or determinative
e) Homosexuality may have multiple components, influences or factors –
including both biology and environment
Nature vs Nurture
a) American Psychiatric Association
“Some people believe that sexual orientation is innate and fixed;
however, sexual orientation develops across a person’s lifetime”
“There is no consensus among scientists about the exact reasons that an
individual develops a heterosexual, bisexual, gay, or lesbian orientation.
Although much research has examined the possible genetic, hormonal,
developmental, social and cultural influences on sexual orientation, no
findings have emerged that permit scientists to conclude the sexual orientation
is determined by any particular factor or factors. Many think that nature and
nurture both play complex roles.”
c) AAP
“Sexual orientation probably is not determined by any one factor
but by a combination of genetic, hormonal, and environmental influences.
d) Association of Gay and Lesbian Psychiatrics
“No one knows what causes heterosexuality, homosexuality, or
bisexuality…there is a renewed interest in searching for biological etiologies
for homosexuality. However, to date there are no replicated scientific studies
supporting any specific biological etiology for homosexuality.”
e) Dr Alan Sanders, Northwestern University
“It is more likely there are several genes that interact with non-genetic
factors, including psychological and social influences, to determine
sexual orientation.”
f) Dr. Gene Robinson, Dir. Of Neuroscience Program at University of
Illinois
“As much as people like to divide themselves into nature or nurture
camps, what genes actually do in the brain reflects the interaction between hereditary
and environmental information.”
Additional: 3 Elements of
Sexuality
·
There are 3 elements of sexuality: Feeling,
Behavior, and Identity
·
“Attraction” is not found in the Bible
·
Temptation, Desire and Lust are found in the
Bible
·
Temptation can lead to sin but not equivalent to
sin
·
Lust is sin
·
Desire is debatably
The speaker’s conclusion
·
It is not about nurture or nature / biological
or environmental but both (complex)
·
Wrong premise: If we can find the cause, we can
fix the problem because it is shifting the responsibility away from us. May
people say/blame parenting as the cause of homosexuality, but this actually misses
the non-environmental and biological factors
·
No matter u think you are born gay, born alcoholic, born
liar…
·
The Bible says YOU MUST BE BORN AGAIN!
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