Human Reproductive Behaviour and Sexual Selection (Relationships)

Question 1

Natural Selection

Answer 1

The gradual process by which nature selects the forms most fit to survive and reproduce in a given environment

Individuals with characteristics that are most suited to the environment are more likely to survive and reproduce

Question 2

Sexual Selection

Answer 2

The selection of characteristics that increase mating success

Sexual selection argue that if a characteristic increases the chances of reproduction then the characteristic will be adaptive because the animal will have more offspring

Question 3

Anisogamy

Answer 3

• humans are anisogamous- they produce gametes (reproductive cells) of different sizes
• male gametes are sperm: contain genetic material, stream line, lots of mitochondria, many of them, enzymes
• female gametes are eggs: contain genetic material, only one released, larger

In anisogamous species, the female invests more energy in reproduction than the male, so it leads to two different types of sexual selection (inter and intra)

Question 4

Inter Sexual Selection

Answer 4

When members of one sex (typically females) choose mates of the other sex to reproduce with based on specific traits

Where females invest more in offspring (time, energy, resources) than males, they are more selective, picking the highest quality mate available

Question 5

Intra Sexual Selection

Answer 5

Competition between members of same sex (usually males) to access or attract member of the opposite sex

Question 6

Sexual Strategies Theory

Answer 6

• Sexual strategies theory (SST) is an evolutionary theory of mating strategies that both males and females adopt under different circumstances.

Females seek males displaying genetic fitness, such as strength, status and resources

Question 7

(Female Intersexual strategies) Fisher (1930)

Answer 7

Sexy Sons hypothesis

• a woman chooses a man because he has a characteristic she wants (e.g. tall male)
• any male children she has will inherit this characteristic and will be more desirable to women
• over generations the characteristic becomes more pronounced- this is known as the runaway process

Question 8

(Female Intersexual strategies) Zahazi (1975)

Answer 8

Handicap hypothesis

• a woman chooses a man with handicaps because it advertises his ability to thrive despite handicaps, demonstrating genetic superiority
• e.g. females finding males attractive who drink or take drugs in large amounts- demonstrated an ability to handle toxins, a sign of genetic fitness

Question 9

(Male Intrasexual strategies) Quantity over quality

Answer 9

• Competition between members of the same sex for access to members of the opposite sex
• in most cases this means males fighting with each other for access to females

Question 10

(Male Intrasexual strategies) Sexual dimorphism

Answer 10

The different characteristics that males and females possess
* males on average 12-15% larger than females
* also includes secondary sexual characteristics
* males: deeper voice, facial hair
* females: breasts, hips, smoother skin

Its a result of male competition and the winner gets to pass on their genes which increases the survival chance of the next generation

Question 11

(Male Intrasexual strategies) Sneak Copulation

Answer 11

• males mate with females other than their partners if given the opportunity as it increases their chances of reproductive success
• women gain from this by having a wider genetic diversity to their children, increasing survival chances
• women can also gain by being in a relationship with a resource-rich male, while copulating with a genetically fit stud

Question 12

(Male Intrasexual strategies) Sperm Competition

Answer 12

• physically size matters for men
• behaviourally- aggression could work
• compete by producing larger testicles bigger ejaculations and faster-swimming sperm

Question 13

Cartwright 2000

(Support for evolutionary explanations for partner preferences)

Answer 13

both men and women prefer symmetrical faces
* symmetry equates with reproductive fitness
* Cartwright also found that women with symmetrical breasts are more fertile
* AND women with symmetrical male partners have the most orgasms
* supports the concept that physical attractiveness is driven by increased ability to reproduce

Question 14

Clark and Hatfield 1989

(Support for evolutionary explanations for partner preferences)

Answer 14

• attractive male and female psychology students (confederates) approached opposite sex strangers on a university campus and asked one of three questions:
  
  • would you go out with me tonight?
  • would you come over to my apartment tonight?
  • would you go to bed with me tonight?
    Question: Female positive response / Male positive response
    1: 50% / 50%
    2: 6% / 69%
    3: 0% / 75%

Supports the idea of intra and inter sexual selection. (men attempt to sleep with as many women as possible whilst women are more selective)

Question 15

Singh 1993 and 2002

(Support for evolutionary explanations for partner preferences)

Answer 15

‘curves in the right places’
* Singh identified waist-to-hip ratio (WHR) as a universally major determinant of attractiveness
* small waist and full hips consistent feature
* optimum WHR = 0.7 (associated with fertility)

shows a cross cultural preference

Question 16

Support for evolutionary explanations for partner preferences

Answer 16

Clarke and Heartfield (1989)
(women selective, men sleep with as many people as possible)

Singh (1993)
(cross cultural preference of 0.7 WHR)

Cartwright (2000)
(physical attractiveness is driven by increased ability to reproduce)

Question 17

Negative evaluations of evolutionary explanation

Answer 17

It cannot explain homosexual partner preferences or couples choosing not to have children as it assumes all relationships are motivated by a desire to reproduce

Alpha bias where sex differences may have been exaggerated