L1 - Evolutionary Explanations For Relationships

Question 1

Sexual selection

Answer 1

• concept by Darwin (1871) - about selecting those characteristics that aid successful reproduction rather then survival
• although characteristics that aid successful reproduction ultimately aid survival
  E.g. male peacock’s tail are signs of genetic fitness, females are more likely to select peacocks with certain tails are more likely to produce robust offspring & will continue in future generations

Question 2

Example of characteristic that’s adaptive

Answer 2

• aggressiveness - it’s an advantage and it acts as a competition against other males for reproductive rights
• if an agressive make reproduces then likely the trait will stay in the population

Question 3

What is the basis of human reproductive behaviour?

Answer 3

Anisogamy - differences between male & female sex cells - gametes
Male gametes - small, mobile, created continuously in vast numbers from puberty to old age, don’t need much energy to be produced
Female gametes - large, static, produced at intervals for a limited number of fertile years - need significant energy to be produced
- means enough males but not enough females
Anisogamy gives rise to two types of sexual selection

Question 4

2 types of sexual selection

Answer 4

• inter-sexual selection
• intra-sexual selection

Question 5

Inter-sexual selection

Answer 5

• between sexes - strategies males use to select females & females use to select males
• preferred strategy of female, quality over quantity
  Male strategies that have evolved seeking to maximise opportunities for mating success include:
• courtship rituals
• size
• sperm competition
• mate guarding
• sneak copulation
  Female strategies that have evolved include:
• sexy sons hypothesis
• handicap hypothesis
• courtship

Question 6

Courtship rituals

Answer 6

Allow males to display genetic potential, through characteristics & resource abilities

Question 7

Size

Answer 7

Males evolved to be bigger, demonstrating strength for success in competition against other males, includes weaponry in some species e.g. antlers in deer

Question 8

Sperm competition

Answer 8

Natural selection acted on males, making them more competitive by producing larger testicles, bigger ejaculations and faster swimming sperm

Question 9

Mate guarding

Answer 9

• males fear being ‘cuckolded (where another male gets their partner pregnant) and spending resources raising another male’s child
• so they mate guard - keep an eye on and remain in close contact with female partners to prevent them mating with other males.
• Buss (1993) believes while men are fearful of partners being sexually unfaithful, females worry about emotional unfaithfulness, due to a fear of their partner spending resources on other females.

Question 10

Sneak copulation

Answer 10

• males mate with other females (as well as their partner) if given the opportunity so that they can increase their chances of reproductive success.
• Women gain from this too as by their offspring having different fathers, increases the wider genetic diversity of their children which in turn increases survival.
• Females can also benefit from sneak copulation by having a rich partner but becoming pregnant from a genetically fit ‘stud’ although if caught she risks being abandoned.

Question 11

Sexy sons hypothesis

Answer 11

devised by Fisher (1930) who argued that females select attractive males as they will produce sons with the same attractive features, increasing their sons and thus their own reproductive fitness.

Question 12

Handicap hypothesis

Answer 12

Zahavi (1975) believes females select males with handicaps, demonstrating superior genetic quality. This may explain females finding males attractive who drink and take drugs in large quantities as they are able to handle them showing genetic fitness.

Question 13

Courtship

Answer 13

• females use courtship to select males on the basis of reproductive fitness, through males demonstrating strength, health and ability to provide resources.
• Prolonged courtship benefits females as they make males invest time, effort and resources, increasing the chances of males not deserting their partners after successful matings.

Question 14

Intra-sexual selection

Answer 14

within (intra) each sex - strategies between males to be the one that is selected, preferred strategy of the male is quantity over quality as they have enough sperm but eggs are rare (like golddust).
- So competition between males to be selected to mate with a female. Thus the winner male passes on these characteristics to their offspring (losers don’t pass their losing’ characteristics because they don’t mate.
- This strategy has given rise to dimorphism (two-forms) - males and females end up looking different because of intra-sexual selection. E.g for males it is likely to be a physical competition which means that size matters - larger males are more likely to win meaning more reproductively successful. However because females do not need to compete against other females for reproductive rights so there is no evolutionary drive towards favouring larger females although youthfulness is important since males prefer more younger (more fertile) females.

Question 15

Consequences of intra-sexual selection

Answer 15

• behavioural consequences that are controversial such as males being more deceitful, intelligent and aggressive as they need to have these characteristics to win the female against another male.
• in order for a male to retain his mate, he must behave aggressively to protect his mate from others therefore a male must show his aggression.

Question 16

Evaluation

Answer 16

strengths
- inter-sexual research support
- further research support
- intra-sexual research support
weaknesses
- reductionist
- social & cultural influences
- doesn’t explain homosexual relationships

Question 17

Inter-sexual selection research support

Answer 17

There is research support for inter-sexual selection - Clark and Hatfield (1989) sent male and female psychology students out across a university campus. They approached other students individually with the question, ‘I have been noticing you around campus. I find you to be very attractive. Would you go to bed with me tonight?’ Not a single female student agreed to this request. However, 75% of males did immediately. This supports the view that females are choosier than males when it comes to selecting sexual partners and males have evolved a different strategy to ensure reproductive success.

Question 18

Further research support

Answer 18

Furthermore, Pawlowski and Dunbar (1999) examined the idea that older women do not disclose their true age in personal advertisements because men judge prospective female partners on their age which is correlated with fertility. This was true of wome between 35 - 50 years of age, implying that women hide their age in order to find high quality partners before their menopause where their reproduction abilities stop. This Study supports inter-sexual selection

Question 19

Intra-sexual selection support

Answer 19

There is also research support for intra-sexual selection - for example David Buss
(1989) carried out a survey of over 10,000 adults in 33 countries. He asked questions relating to a variety of attributes that evolutionary theory predicts about intra-sexual selection. He found that females placed greater value on resource-related characteristics such as money and ambition than males did. Whereas males valued physical attractiveness and youth (as signs of good reproductive capacity) more than females did. This supports the idea that women compete with other women and men compete with other men to gain a sexual partner for different reasons

Question 20

Reductionist

Answer 20

One problem with evolutionary explanations for partner preferences is that it assumes that one strategy is adaptive for example all males looking for younger females due to them being more fertile and that all females are looking for a ‘stud’ - is too simplistic - reductionist. For example, there are other factors that might be relevant such as if somebody wants a long term or lifetime relationship. Buss and Schmitt (2016) argue that both males and females who are looking for long term relationships are much choosier looking for partners that are loving, loyal and kind. This is clearly much more complex than the simple explanation put forward by evolutionary theory about sexual selection.

Question 21

Social and cultural influences

Answer 21

Another weakness with evolutionary explanations for partner preference is that social and cultural influences have been underestimated. Partner preferences over the past century have been influence by changing social norms of behaviour. These develop much faster than evolution and have come about due to cultural influences such as contraception. Furthermore, women greater role in the workplace means that they are no longer dependent on men for financial support - this means according to Bereczkei et al (1997) that this social change means women’s mate preferences have changed as they no longer rely on men being breadwinners. Therefore the evolutionary theory must account for social and cultural influences otherwise it is incomplete.

Question 22

Homosexual relationships

Answer 22

Finally, sexual selection theory as an evolutionary theory cannot explain partner preferences for gay and lesbian individuals - this is because homosexuals when choosing their partner are not looking for genetic fitness - something which is key to heterosexual relationships although they may assess other qualities relevant to the caring of offspring. Furthermore Lawson et al (2014) looked at personal ads placed by both heterosexual and homosexual individuals (describing what they are looking for in their partner and what they are offering). They found that the preferences of homosexual men and women differed as they did with heterosexual men and - men emphasised physical attractiveness and women emphasised resources although the study did conclude that homosexual and heterosexual relationships are not similar in choosing partners.