2.7 – Genetics and Behaviour

How many chromosomes pairs are in every human cell? Where does each one in the pair come from? 23 pairs. One set from each of the parents

Define genotype. The genetic makeup of an individual Define phenotype? What factors make up a person’s phenotype? The observable characteristics of an individual. Phenotype is derived from the interaction of genotype and the environment throughout development.

What is PKU? How does it help us understand how genes and genetic screening work and what does it NOT tell us? Phenylketonuria – a condition that results from the lack of an amino acid that breaks down phenylalanine. This causes a build up of phenylalanine in the body to lethal levels. PKU shows us that genes can be identified with clear roles in the body and that behaviours can be altered to compensate for this. This also causes an overemphasis on genetic factors and invalid behavioral changes to be considered.

How can adoption studies help psychologists understand the role of genetics in behaviour? Birth mother phenotypes can be compared to offspring phenotypes to isolate environmental factors from genetic factors.

Summarize the findings of Heston, Heston (1966) found that the incidence of schizophrenia between birth mothers and adopted children had 10 times the rate than the regular population. Therefore schizophrenia has a strong genetic determinant.

How can twin studies help psychologists understand the role of genetics in behaviour? Twin studies enable researchers to compare monozygotic phenotypes to dizygotic phenotypes to isolate genetic and environmental factors.

Summarize the findings of Bailey and Pillard, Bailey and Pillard (1991) compared the concordance rates for homosexuality between monozygotic twins versus dizygotic twins. DZ – 22% concordant for homosexuality MZ – 52% concordant for homosexuality Therefore there is a strong genetic component for homosexual behaviour

What are the limitations of making conclusions from data obtained in adoption and twin studies? The data cannot be located – function cannot be determined Ethical concerns – how is a subject treated once genetic propensity has been identified?

2.8 – Evolutionary Psychology

Explain in your own words, the way evolutionary behaviour works as described in the first paragraph. If, from the last section, we determine that the behaviour of people has some origins in our genotype, and if we accept evolution and natural selection as principles, then it must be the case that certain fundamental behaviours people have must have been adaptations for successful survival and procreation. Therefore, we can try to explain our behaviours in terms of their potential adaptive value to the species.

How does homosexuality conflict with evolutionary psychology? What are some possible explanations for this? If behaviour has its origins in reproductive advantages, then homosexuality should not exist as it has no possible reproduction involved. This can be explained through evolutionary psychology in that there must be some advantage to the behaviour – possibly in a group setting, sharing and managing resources, co-operation, or other non-individual gain for the group. Other explanations are that somehow, homosexual behaviour increases attractiveness to potential mates of the opposite sex.

What were the conclusions reached by Zeitsch et al. 2008? Zeitsch et al (2008) conducted questionnaires with 4904 identical twins regarding sexual orientation, opposite-sex partners, and gender identity. He determined that sex-atypical gender identity was associated with having more heterosexual partners and this trend was increased when one twin was a homosexual. The conclusions is that homosexual genetic predisposition without identifying as homosexual carried advantages to potential heterosexual partners.

What is HAT? Explain how it works. Homicide Adaptation Theory – humans have evolved with a psychological adaptation for killing other humans. The propensity to kill would have advantages for eliminating potential competition for mates or resources or threats to offspring.

How does Durrant (2009) disagree with HAT? Durrant (2009) argues that the predisposition to kill may no longer carry any kind of advantage and may be an evolutionary remnant. He states that a cost-benefit analysis shows that the potential risk of killing or murder outweigh the potential advantages and therefore are not useful adaptations that would be passed on.

Get into groups of 3 to 4 One member of the group must come to the front and receive a study in evolutionary psychology. Another member must go to the side table and retrieve a piece of flipchart paper and a marker.

As a group – you are required to analyze the study you have been given and answer the following questions on your flipchart paper: 1) Who is author and what is the year of the study? 2) What is the title of the study? 3) What is the behaviour under examination or explanation in the study? 4) What, briefly, was the method used by the authors? 5) What is the perceived evolutionary purpose of the behaviour or the evolutionary advantage gained by the behaviour explained by the author(s)?