Psychology of Sexuality
Biological Basis of Homosexuality:
- Code for sexual differentiation
- You are born male or female in body and brain if all goes well
- But if that doesn’t happen – you may not be completely sexually differentiated
- There is some incompleteness of the brain in sexual differentiation in sexual dysmprohic
areas of the brain – structural differences in gay men and gay women verse their straight
counters. The things that happen to make you fully your ender- don’t happen properly
prenatally – the bran is altered and becomes slightly sex atypical.
- Prenatally – men have to be defeminized and masculinized- physically and in brain.
Fetuses will come out morphologically female if this does not happen. In sexual
orientation for men – genetic variants as well as other things – causing sexual
differentiation to be incomplete- insufficiently defeminized and masculinized- genes are
coding for insufficient use of masculinizing and defeminizing hormones available
prenatally- this only affects certain areas of the brain. But think there are genes coding for
- As female – opposite – you get defeminized and masculinized somewhat. There is
incorrect use of prenatally available hormones leading them to be slightly defeminized
and masculinized. Incomplete sexual differentiation permanently affects the brain
- Organizational – activational hypothesis: Organized prenatally – activated at puberty
when we start being interested in people as sex objects.
- Some of the biological processes that help us set sexual orientation later in life are
- Morphologically everything is right- but neutrally things have been slightly set ascue.
Probable genetic markers:
- Chromosome 7: found specifics associated with male sexuality. X chromosome
differentiated as others as well.
- Hard to find all genes involved. - We have been able to identify some genes involved.
- Family studies.
- Compare ho similar MZ twins are – compared with DZ twins- siblings.And baseline of
- Given MZ tin gay – what is likelihood you are? – very high compared to everyone else.
More than 50/50 chance – but environment plays a role because not 100%
- Surprisingly – we see same pattern in females – suggesting genes are involved in male
and female sexuality.
If this is genetic – how could homosexuality be evolved
- Could be every gay person has a mutation in a group of genes – but this is not a satisfying
- But mutation partnered with evolutionary process- how do genes for homosexuality
survive given they do not reproduce themselves in the vast majority – how do the genes
get passed along
- Two types of theories proposed- some based on gene variance involved – being good for
reproductive success unless you get too many of them in which you are gay.
- Some look at kin selection and inclusive fitness- some have gay genes without all of them
and are not gay- but simply banking on their reproductive success your gay gene stays in
- Gene based theories: suggest many genes for homosexuality and these genes if
combined in right configuration – then you are gay and if not you simply have gay genes
beneficial in some way. Borrow from simpler disease- cicle cell enemia – painful and
unpleasant and can limit reproductive success- but survived across time especially in
populations dealing with malaria – which bursts blood vessels and you lose your red
blood cells. If you have one or two alleles coding for cicle cell – you get protection
against malaria even if you get infected. If you get both alleles for cicle cell – you have
cicle cell and you have these blood vessels. Malaria is horrible, cicle cell is horrible – but
protection against malaria is worth cycle cell survival.
- places with a lot of malaria – likeAfrica – a lot of cicle cell. That is because they can be
beneficial. Idea genes can be wonderful and horrible – borrowed by theorists trying to
understand the genetic survival of homosexuality. Two Gene Based Theories:
- Rohman and Wilson: argued the presence of gay genes in population due to the fact Dads
pas them along to offspring – dads who don’t have all of them and hence are straight pass
them on to recombine with moms genes to result in some sons being gay. Homosexuality
stays in gen