Mating and Attractiveness. Flashcards
Who introduced the theoretic foundation of the theory of parental investment (PI) and sexual selection?
Trivers’ 1972
Sexual selection involves two main processes:
- Intersexual selection (choice).
- Intrasexual competition.
Adaptations designed by intersexual selection (animals).
- male peacock, mandril. - designed to appeal to females. - can impede survival - carrying around huge tail.
- Hermit crabs, male deer antlers. - naturalised weaponry, protection, competition. - can impede survival, carrying around antlers, and can get stuck in trees.
Exceptions (that prove the rule):
In species where males have higher PI (e.g. seahorses, phalaropes), females tend to be more competitive and less choosy, and to have more mates.
What does a decline in human sexual dimorphism over course of evolution suggest?
Suggesting a trend towards increased biparental care, vibrant monogamy.
Sperm Competition.
- Chimps, of all the primates, have the largest testes to body size.
- Due to their promiscuous breeding system, some male chimps have large testes, providing an advantage.
- It is an advantage because they have more sperm production because as the female chimps have multiple male partners, and will have the sperm of multiple males inside her reproductive tract, there will be competition within the reproductive tract
- Gorillas have a small testes to body ratio - they do not need such large testes because the females aren’t mating with other males, meaning there is less competition and you won’t need to produce as much sperm.
Humans are flexible strategists…
so all strategies are all equally ‘natural’.
Everything is natural.
What circumstances does the best strategy depend on?
- Individual characteristics like mate value, life expectancy.
- Environmental factors like harshness of environment (need for bi-parental care) - - - male-female sex ratio.
- human legal environment (in most Western industrialised cultures, polygamy is illegal).
Flexible strategizing & strategic pluralism:
- Trade-offs that mating strategies entail, e.g. females choosing ‘good genes’ male versus ‘good provider’.
- Choose good provider when male parental investment (i.e., bi-parental care) is more crucial. - when it’s a harsh env, bi-parental care is important.
What does ‘Sociosexuality’ (or ‘sociosexual orientation’) measure?
individual interest in short-term mating.
- individual difference in the willingness to engage in sexual activity outside of a committed relationship
Where, what and who has higher socio-sexuality? (Schmitt, 2005).
- higher in nations with fewer men and less ‘hardship’,
- cross-culturally, men have higher mean socio-sexuality.
Important socio-sexuality findings -
- when life is harder, that is when two parents are going to come together and consistently invest.
- If there are signs of hardship, such as mortality, child malnutrition, these will be negatively correlated, and people will be less enthusiastic about having short-term relationships with multiple partners, and more focused on bi-parental care and monogamy.
- If there are positive indicators, such as living in a wealthy country, you’re going to have a higher sense of sexuality, easier access to resources and provide for your offspring with health care.
What happens if there are more males there are than females in terms of socio-sexuality?
the more female-like the dominant mating system becomes. (long-term, bi-parental).
- females become more =in demand’ and valuable.
- Schmitt - cross-nationally, male AND female SOI was higher when male to fem sex ratio is lower
What are three theories Buss mentions (in order of empirical support).
- Female fertility (genetic theory), as explanation for homosexuality in males and females.
- kin altruism
- alliance formation
Female fertility (genetic theory), as explanation for homosexuality in males and females -
- Idea is that there is a gene that increases female sexuality and sexual desire towards males, same thing in males, which eroticises the same sex (males).
- The benefit for female reproduction is so great that it offsets the cost of having this gene present in males.
- If these genes are present in one sex and have a negative effect on reproduction, they may compensate for that by having a positive effect on the other sex.
Kin altruism
- Homosexual are more likely to remain ‘helpers of the nest’.
- Will invest more in the offspring of close kin, which via kin selection could lead to the genes for homosexuality.
Alliance formation
- The idea that homosexuality is used as a way to still have fine alliances in some cultures.
- You see this in bonobo chimps - seems to be a way of bonding - not necessarily as sexual partners.
female orgasm, as a by-product.
- This analysis is specially designed to solve a specific kind of adaptive problem.
- He believed it is a by-product, that the female orgasm is a bi-product of the male orgasm.
- Because the male orgasm is motivating the male to achieve orgasm, which is ejaculation, needed for reproduction.
- Why would you need to instil that motivation in the female? - because it is not necessary for reproduction.
How did men’s PI help in EEA societies?
Secure food, territory.
Build shelters, tools.
Physically defend against enemies/predators.
Acquire social support (e.g. shared food, medical help) via kin, alliances, social status.
Rear children (instruction, discipline).
Voice family’s interest in the social/political sphere.
Receiving PI in the form of material resources are more important to mothers than to fathers.
- women place greater emphasis on the economic resources of mates.
‘Robust finding in a vast variety of cultures’ (ability to procure and retain resources) - females rank it on average twice as high as males. - This preference increases in females who are more independently wealthy.
Women’s preferences in men -
- receiving pi in form of material resources
- high social status
- willingness to invest
- Older men
- dependability and stability
- athletic
Preference for men of high social status.
Again, this is a robust cross-cultural difference.
EEA-like societies are sometimes described as ‘egalitarian’, and indeed are in many ways.
However, status differences exist and are associated with access to resources and wives.
Older men
In all 37 cultures (Buss, 1989), women tended to prefer older men, though not too much older (mean of 3.5 years older, range about 2-5 years).
Older men have higher status, more resources, and expertise.
But if too old, it raises issues of survival and health.
ability to invest, willingness to invest
Women are sensitive to cues that a potential mate interacts well with children (men are not; La Cerra, 1994)