Evolutionary Explanations (relationships) Flashcards
What is sexual selection?
When a characteristic has been passed on but doesn’t necessarily aid survival. Rather, these characteristics have been passed on to indicate genetic fitness instead.
Why is sexual selection important?
Because females looking for a mate will select males with desireable traits as they are more likely to have offspring with the same indicators of ‘genetic fitness’.
Give an example of a genetic fitness characteristic
Male peacocks’ tails have got larger across generations to the point where some can’t stand up properly.
Give an example of an adaptive behaviour
Aggressive behaviour can also be considered as an adaptive behaviour because males can fight with other males to secure a mate.
What happens when aggressive behaviour is an adaptive behaviour?
These aggressive characteristics are passed on to their offspring if they are determined by genetics and so continue across generations.
What is anisogamy?
When there are differences between male and female sex cells.
Male sex cells
Sperm is produced in large quantities, quickly replenished, and produced continuously from puberty until old age.
Female sex cells
Eggs are limited. Women are born with a limited number of eggs that are only released at certain points of the menstrual cycle. They are only fertile from puberty to menopause.
Why do females put more energy into reproduction than males?
because egg needs to be released at the right time and then they carry the child for 9 months.
Who is a rarer resource?
Fertile women are rarer.
What has anisogamy led to?
Two types of sexual selection in humans to tell us about partner preferences.
What are the two types of sexual selection?
Inter-sexual selection and Intra-sexual selection.
What is inter-sexual selection?
Where traits increase ‘attractiveness’ and/or get members of the opposite sex to mate with them.
Why is inter-sexual selection useful for females?
Because female reproduction involves greater investment of time, energy and resources to raise a child so females need to be more careful when choosing a partner.
What was Fisher (1930)’s hypothesis?
‘Sexy sons’ hypothesis.
Who came up with the ‘sexy sons’ hypothesis?
Fisher (1930)
What is the ‘sexy sons’ hypothesis?
A female who mates with a male that has a certain attractive characteristic, will have offspring that inherits this ‘sexy’ trait.
What do females look for in a partner?
A male that will provide the best pool of genetics for her offspring to have the best chance of surviving and passing on their genes.
What do males look for in a partner?
Females that look youthful because this indicates fertility. e.g. a narrower waist and rosy cheeks.
What is intra-sexual selection?
Where traits allow an individual to compete with members of the same sex for access to mating opportunities.
What is dimorphism?
The fact that males and females look very different to each other.
Why does dimorphism occur?
Because males are stereo typically taller and have a larger build as these traits give them an advantage when competing against other males and so make them more likely to be selected by females for reproduction therefore these traits are passed on.
Who conducted research that supports the evolutionary theory?
Clark and Hatfield (1989)
David Buss (1989)
Outline Clark and Hatfield’s Research
They asked male and female student volunteers to approach opposite sex students individually on campus and proposition them for sex.
What question was asked during Clark and Hatfield’s research?
“I’ve noticed you around the campus. I find you very attractive. Will you go to bed with me tonight?”
What were the findings in Clark and Hatfield’s research?
Significant gender differences in the responses to the question. 75% of male students agreed however, not a single female said yes.
Why does Clark and Hatfield’s research support the evolutionary theory?
It supports the idea of inter-sexual selection, in that females will be more selective when choosing a partner and that males opt for a different strategy.
When was Clark and Hatfield’s research conducted?
1989
Outline David Buss’s research
He surveyed over 10,000 adults across 33 countries.
What were the findings from David Buss’s research?
Females across all cultures put importance on characteristics that signal ability to provide resources, in a partner. On the other hand, males preferred women who were younger and more attractive as this suggests high fertility.
Why does David Buss’s research support the evolutionary theory?
Supports the sex differences in sexual selection and how these may have evolved to develop through inter-sexual selection as a result of competition within the sexes.
Name the reductionist limitation of the evolutionary theory
It ignores the role of social and cultural factors in determining partner preferences.
How have social norms changes partner preferences?
Increase in women working, so dependence on men for resources has lessened.
Contraception is now readily available to stop unwanted pregnancies. So a woman’s youthfulness and attractiveness signalling fertility would be pointless if she were on contraception that inhibits her chances of reproducing.
Why does ignoring social and cultural factors limit the evolutionary theory?
because it seems unlikely that evolution has the only influence on partner preference, if a change in social and cultural norms have also influenced partner preference.
Name a further limitation of the evolutionary theory (not reductionist)
It cannot explain partner preferences across homosexuals.
Why does the evolutionary theory not work for all relationships?
The theory explains preferences across a male and female relationship, relating to reproductive success. Homosexual relationships do not have the underlying aim of reproduction, so these theories cannot explain the other strategies they have.
Why does not being able to explain partner preferences in homosexuals limit the evolutionary theory?
It questions the validity of the theory in explaining all types of relationships.
