Lesson 1 - Evolutionary explanations for partner preferences

Question 1

Darwin (1871)

Answer 1

Outlines the idea of sexual selection; selection is based on characteristics that aid successful reproduction rather than survival (although successful reproduction will lead to survival)

For example, a male peacock’s tail is a sign of genetic fitness. Therefore the mating with these males will lead to robust offspring

Question 2

Anisogamy

Answer 2

Refers to a form of sexual reproduction involving the fusion of two different gametes (sex cells).

These gametes differ in size and often, in form or function.

In most cases, the larger gamete is immobile and is called the egg (female gamete), while the smaller, mobile gamete is the sperm (male gamete).

Forms the basis of human reproduction, and gives rise to intrasexual and intersexual selection

Question 3

What is intersexual selection?

Answer 3

These are the strategies that males use to select females and vice versa, between the sexes

Question 4

What are the male intersexual strategies?

Answer 4

• Courtship rituals
• Size
• Sperm competition
• Mate guarding
• Sneak copulation

Question 5

Courtship rituals

Answer 5

Intersexual strategy for males

Allows males to display genetic potential, through characteristics and resource abilities

Example - a male human may show off their money or strength

Question 6

Size

Answer 6

Intersexual strategy for males

Males have evolved to be bigger, demonstrating strength and robust genetic fitness and success in competition with other males

Example - deers develop antlers, a form of weaponry/defence

Question 7

Sperm competition

Answer 7

Intersexual strategy for males

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

Example - males with larger testicles and bigger ejaculation are more likely to be able to reproduce successfully

Question 8

Mate guarding

Answer 8

Intersexual strategy for males

Males fear being cuckolded (when another male gets their partner pregnant)

Males therefore keep an eye on their female partners to prevent them mating with other males

Buss (1993) supports this, believing that men fear cuckolding and women fear their male spending resources on other females

Question 9

Sneak copulation

Answer 9

Males partner with their partner AND other females if given the chances to increase their chances of successful reproduction

Females gain from this, as by having many fathers of their children, this increases genetic diversity and survival

Question 10

Female intersexual strategies

Answer 10

• Sexy sons hypothesis
• Handicap hypothesis
• Courtship

Question 11

Sexy sons hypothesis

Answer 11

Intersexual strategy for females

Devised by Fischer (1930), which states that females select males based on attractiveness so that their sons adopt the same features and reproductive fitness

Question 12

Handicap hypothesis

Answer 12

Intersexual strategy for females

Zahavi (1975) believes that females select males with handicaps, like excessive drug or alcohol use, to show that they are can withstand this and shows genetic fitness

Question 13

Courtship

Answer 13

Intersexual strategy for females

Prolonged courtship (basically dating) benefits females as they make males invest time and resources and this makes them less likely to leave after successful matings.

Question 14

What is intrasexual selection?

Answer 14

Selection within each sex. For example, males will compete with each other for selection.

This has lead to dimorphism (differences in men and women). For example, as there is likely to be physical competition between males, men are more likely to be larger, but as there is no competition for selection between females, they may not look different.

Has behavioural consequences such as over-aggressiveness

Question 15

Strengths of evolutionary explanations

Answer 15

• Clark and Hatfield (1989) sent male and female students out across a university campus. They were instructed to approach students individually and ask them ‘I have been noticing you around campus. I find you to be very attractive. Would you go to bed with me tonight?’ No women agreed to this, but 75% of males did. This supports the idea that females are choosier than males and males have evolved different strategies to ensure reproductive success
• Pawlowski and Dunbar (1999) examined the idea that older women do not disclose their age because men judge partners based on age and fertility. This was shown in women of 35-50. This supports inter-sexual selection
• Buss (1989) carried out a study of 10,000 people across 37 cultures of what they want in a partner. Females valued money and resources while males valued fertility and youthfulness. This supports the idea that women compete with other women and men compete with other men.

Question 16

Weaknesses of evolutionary explanations

Answer 16

• Other factors may be relevant in whether a person wants a long term relationship with someone. Therefore this idea is reductionist. Buss and Schmitt (2016) found that males and females were more inclined to choose partners who were loving, loyal and kind. This is obviously more complex than the evolutionary explanation about sexual selection.
• Another weakness is social and cultural influences have been underestimated. Changing social norms influence cultural changes and this in affects partner choice. For an example, changes in contraception norms have changed the dynamic of sexual selection. Also , women have a greater role in work so they are less financially dependent on men.
• It does not account for homosexual couples. They are not looking for genetic fitness, as they are not interested in the caring of offspring. Lawson et al (2014) found that the personal ads of both homosexual and heterosexual people are different, showing that they are not similar when choosing partners.