Sexual Selection & Human Reproductive Behaviour Flashcards
What is the definition of sexual selection?
Evolutionary explanation of partner preference
Attributes/behaviours that increase reproductive success passed on & may become exaggerated over succeeding generations of offspring
What is the definition of Human Reproductive Behaviour?
Any behaviours which relate to opportunities to reproduce & thereby increase survival chances of our genes
Includes evolutionary mechanisms underlying our partner preferences, like mate choice & mate competition
What is the human reproductive behaviour theory?
Males produce approximately 100 million sperm per ejaculation, meaning they have potential to recreate many times
Females born with limited number of eggs, with 1 released per month for 35-40 years, thus they have fewer chances to reproduce
Due to this:
Males feel more competition with other males to find suitable females
Females more selective over males possessing best characteristics to pass on to limited offspring
What is the sexual selection theory?
Male’s best chance of success = have sex as much as possible with as many women to increase opportunities to reproduce & seek out females showing signs of fertility
Female’s best chance of success = choosing mates showing signs of superior genetic fitness & display signs of ability to provide resources
Name male mating strategies
Mate-guarding: Protective over mate to prevent other males getting her pregnant & thus using their resources to raise another man’s offspring
Sneak copulation: Males may have sex with other females in absence of partner to increase chance of passing genetic material to more offspring
Size & Appearance: Males evolved larger & some species developed physical attributes to increase appearance of strength to females
Name female strategies
Sexy sons: Females seek out attractive males so sons they produce will be equally attractive & continue to pass on genes to another generation
Courtship: Make male spend time & resources in build up to relationship so female can check sustainability for reproduction
Handicap hypothesis: Zahavi (1975) argued females seek males with signs of handicap indicating strength of genes over adversity
Outline anisogamy
Differences between male & female gametes
Male gametes = small, mobile, created continually in vast numbers from puberty to old age & don’t require lots of energy to produce
Female gametes = relatively large, static, produced at intervals for limited number of fertile years & require huge energy expenditure
Consequences of this are:
Mate selection: Fertile women are rare resource
Partner preferences: Explain inter and intra-sexual selection
Outline inter-sexual selection
Quality > quantity = preferred strategy of female as ova rarer than sperm & require greater energy to produce
Consequences of making wrong choice of partner more serious for female, thus female’s optimum mating strategy = select genetically fit partner able & willing to provide resources
This leaves males competing for opportunity to mate with fertile female
Outline intra-sexual selection
Quantity > quality preferred strategy of male
Refers to competitions between males to mate with female
Winner gets to reproduce & pass on genetics to offspring contributing to victory
This causes dimorphism - obvious differences between genders
Larger males have advantage, thus more likely to mate
Females don’t compete for reproductive rights, thus no evolutionary drive towards larger females
Evaluate evolutionary explanations of partner preference
STRENGTH: Research Support (Buss)
Buss (1989) surveyed over 10,000 adults in 33 countries, asking questions relating to age & variety of attributes evo theory theory predicts important in partner preference. He found females valued resources more than males did. Males valued reproductive capacity like looks & chastity & younger mates.
Reflect sex differences in mate strategies due to anisogamy, supporting predictions of partner preference from sexual selection theory & can be applied various cultures
STRENGTH: Research Support (Clark & Hatfield)
Male & female psychology students asked ‘I’ve been noticing you around campus. I find you very attractive. Would you go to bed with me tonight?’ No female agreed, but 75% of males did.
Supports theory as females choosier when selecting partners & males evolved different strategy for reproductive success.
LIMITATION: Ignores social & cultural influence
Partner preferences over past century influenced by rapidly changing social norms of sexual behaviour - these develop faster than evolution. Women’s greater role in work mean no longer dependent on men to provide.
Thus, mate preferences outcome of combination of evol & cultural influences. Any theory failing to account for both is limited explanation
