Transcript 2.8 – Evolutionary Psychology

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,
1966.
• 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, 1991.
• 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
• 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)?