Evolutionary theory

• The basis of this theory is that every species has one aim to reproduce and pass on their genes.
• For our ancestors, mating was a complex business because:

  Selecting the right mate 

  out-competing any rivals 

  engaging in the correct behaviours for successful conception. 

  Child rearing.
• Sexual selection: some features are more attractive than others to the opposite sex. These features are more likely to attract a mate, which would then lead to reproduction, and those genes would then be passed onto the next generation.

  These leads to certain traits becoming even more exaggerated through generations of offspring. These traits then provide an advantage over other traits when it comes to attracting a mate. This includes secondary sexual characteristics.
• Evolutionary explanations for partner preferences are important because they tell us who is likely to be included or excluded in mating. The characteristics that are to some extent inherited (like physical attractiveness and intelligence) will then appear in the population and future generations more frequently -sexual selection.
• Sexual selection: attractive

  Taller males: women attracted to taller males and tall males therefore reproduce, passing on their genes to produce tall sons. This makes 'height' exaggerated in males as an attractive quality (12 - 15 % larger than females).

  Males> deeper voice, facial hair

  Females > breasts, hips, smoother we call these differences in males and females sexual dimorphism.
• Anisogamy:

  • refers to the differences in males and female sex cells (gametes) these differences are very obvious in humans.
• Anisogamy:

  Males-millions of sperm, created continuously,require little energy to produce.

  Females - large ova (eggs) Limited in supply (only during fertile period ) only produced in small numbers, requires a huge investment of energy.
• consequence of anisogamy is that there are plenty of fertile males, but a fertile female is a rare resource. means that there are two different mating strategies, and as a result two different types of sexual selection.

  Males must try and mate with as many females as possible, as minimal effort is required to produce sperm and they do not to put effort in during or after conception. leads to preferences for youthful and fertile potential females.

  Females must be choosy to make sure they attract the most secure mate possible- someone who will provide resources to care for their offspring.
• Intersexual selection:

  Preferred strategy of females: quality over quantity.
• Intersexual selection: Member of 1 sex evolve preferences for desirable qualities in potential mates. Members of opposite sex who possess these characteristics will gain mating advantage over who don’t. preference by one sex, determines areas other sex must compete. Females make greater investment of time,energy,commitment before, during/after birth. Females extra choosy,has more to lose if chooses wrong partner. optimum mating strategy choose a partner that is able/willing to provide resources. males competing to mate with fertile female will produce more males-unattractive features die out.
• Intrasexual selection:

  Male strategy: quantity over quality.
• Intrasexual selection:Members of one sex (usually males) compete for access to the other. The victors then mate, and then the characteristics are passed into offspring (losers don’t mate then these traits are not passed on). Whatever traits lead to success in these same-sex contests will be passed on to the next generation. intrasexual selection often involves fighting, whatever characteristics involve the success will become more widespread in that gene pool. E.g larger and stronger males will have an advantage which has given rise to dimorphism (the obvious differences in males and females)
• A weakness is that it ignores the role of culture on sexual behaviours. Social norms often dictate changes in sexual behaviour, but evolutionary changes take a long time to develop (social norms develop faster than evolutionary changes). Bereczkei argue that females preferences have now changed since women are more equal in the workplace and no longer have to rely on males for resources. This suggests that a combination of evolutionary and social/cultural influences need to be considered which this explanation fails to do. 
• A strength is that there is supporting research evidence for mate preferences related to anisogamy. Buss surveyed 10,000+ adults in 33 countries and asked Qs relating to partner preferences. Found that females placed greater importance on resources related to characteristics and males valued reproductive capacity. This suggests that there are sex differences in mating strategies due to anisognamy as it supports the prediction of sexual selection theory. 
• A strength is that there are further evidence comes from research into intersexual selection. Clarke and Hatfield sent males and females psychology students into a university campus and instructed them to approach pps with a question, propositioning a member of the opposite sex for sex. 75% of males agreed to except with the pps whereas 0% females did. This supports sexual selection theory because it suggests females are more choosy than males when it comes to selecting a sexual partner and they have evolved different mating strategies to secure reproductive success 
• A weakness is there is the issue of gender bias. The theory emphasises difference between males and females. This may be an exaggeration of how males and females behave differently, especially given that society has changed and roles and behaviours of women have changed. It is plausible to argue that males and females seek some similar attributes such as reproductive