Sexual selection
- Evolutionary explanation of partner preference
- Genes selected that promote survival (natural selection) or successful reproduction (sexual selection)
Darwin
- Concept of sexual selection
- Females select males with characteristics are more likely to produce robust offspring
Adaptive traits
Eg aggression
Provide an advantage for a male over competitors for reproductive rights
Human reproductive behaviour
- Any behaviours which relate to opportunities to reproduce
- Increasing chances of survival of our genes
Anisogamy
- Differences between male and female sex cells
- Male gametes - small, highly mobile, created continuously is vast numbers, no energy to make
- Female gametes - large, static, produced in intervals for a limited number of fertile years, sig investment of energy
- Gives rise to two types of sexual selection
What is one consequence of anisogamy
- No shortage of fertile males but a fertile female is a much rarer resource
Inter-sexual selection
- Between the sexes
- Preferred strategy of females
Dimorphism
- Males and females end up looking very different because of intra-sexual selection
- Females don’t need to compete but youthfulness is more important
Examples of dimorphism
- Men being bigger
- Women having large waist-to-hip ratio
Intra-sexual consequences
- Behavioural consequences
- Characteristics that are favoured and passed on - allow men to outcompete rivals
- Include deceitfulness, intelligence and aggression
- Selection of aggressiveness in males
Research support - inter-sexual selection + counterpoint
- Clark and Hatfield
- Sent male and female students across uni campus and approached other students to ask for sex
- 0% of women said yes, 75% of men said yes
- Females are choosier than males
- Males have evolved a different strategy to ensure reproductive success
- Simplistic
- Sexual strategies theory (Buss and Schmitt) - both males and females adopt similar matching strategies when seeking long-term relationships
- It is more complex and nuanced view of how evolutionary pressures influence partner preference which takes account the context of reproductive behaviour
Research support - intra-sexual selection
- Support the predictions of sexual selection theory
- Buss - survey of over 10,000 adults in 33 countries
- Variety of attributes that evolutionary theory predicts are important in partner preference
- Females placed greater value of characteristics
- Men value physical attractiveness and youth more than women
- Findings reflect consistent sex differences in partner preferences and support the predictions from sexual selection theory
Social and cultural influences underestimated
- Limitation
- Theories overlook influences of social and cultural factors on partner preference
- Partner preferences - develop faster than evolutionary timescales imply - due to cultural factors eg contraception
- Women’s role in workplace
- Bereczkei et al - social change has consequences for women’s mate preferences - no longer resource-oriented
- Partner preferences today - likely due to combination of evolutionary and cultural influences - any theory that fails to account for both is a limited explanation
Sexual selection and homosexuality
- Cant explain preferences in homosexuality
- But homosexual preferences differ just like heterosexuals
- Lawson et al - looked at personal ads placed by heterosexual and homosexual men and women
- Preferences of homosexual men and women differ just as they do in heterosexual men and women
Survival of the fittest
The best adapted to the local environment - any characteristic or behaviour that increases the chance that an individual will survive and reproduce would be passed onto future generations
Natural selection
Major process that explains evolution whereby inherited traits that enhance an animal’s reproductive success are passed on to the next generation - animals without such traits are less successful at reproduction and their traits are not selected
Survival of the sexiest
Not necessarily strongest or most intelligent - eg peacock tails
Adaptive / adaption
Any physical or psychological characteristic that enhances an individual’s survival and reproduction and is thus likely to be naturally selected - such characteristics are passed on to future generations
EEA
- Species first emerged as a distinct species from ancestor
- Physical and behavioural characteristics of a species will be suited to EEA
