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November 15 - Lecture 30.docx

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McMaster University
Jennifer Ostovich

Psychology of Sexuality Biological Basis of Homosexuality: Genes: - 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 this. - 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 incomplete. - 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. Concordance rates: - Family studies. - Compare ho similar MZ twins are – compared with DZ twins- siblings.And baseline of population. - 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 argument. - 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 pool - 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
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