Sexual selection and human reproductive behaviour

Question 1

SEXUAL SELECTION

Answer 1

Evolutionary explanation of partner preference.

Attributes or behaviours that increase reproductive success are passed on

Attractive characteristics

Characteristics that provide an advantage over
competitors for reproductive rights

Question 2

ANISOGAMY

Answer 2

The differences between male and female sex cells.

Male gametes are small, mobile and occur in vast
numbers

Females gametes are large, static and occur in intervals

A consequence of anisogamy for mate selection is that there is no shortage of fertile males, but a fertile woman is a ‘rare’ resource

Question 3

Anisogamy gives rise to two mating strategies

Answer 3

Intra sexual selection (mate competition)
Competition within a sex

Inter sexual selection (mate choice)
Preference for traits in the opposite sex

Question 4

INTRASEXUAL SELECTION (MATE COMPETITION) 1

Answer 4

Members of one sex compete with each other for access to members of the opposite sex.

Preferred strategy for males

Whatever traits lead to successful mating in these contests will be passed on to the next generation.

Question 5

INTRASEXUAL SELECTION (MATE COMPETITION) 2

Answer 5

A male’s optimum reproductive strategy is to mate with as many females as possible

A behavioural consequence of this competition for
fertile mates is a distinct preference for youth, and a
sensitivity to the indicators of youth and fertility

Question 6

INTERSEXUAL SELECTION (MATE CHOICE) 1

Answer 6

The preferences for certain traits in the opposite sex.

Preferred strategy for females.

The preferences determine the areas in which the opposite sex must compete.

These indicators become signals to the opposite sex that they have “good genes” likely ;

a) to produce successful offspring

b) to be able to give protection and support to offspring.

Question 7

‘Sexy sons hypothesis’

Answer 7

A female mates with a male who has a desirable characteristic, and this ‘sexy’ trait is inherited by her son

His increases the likelihood that successive generations of females will mate with her offspring

Question 8

SEXUAL SELECTION AND LONG TERM MATE
PREFERENCE

Answer 8

Females are attracted to mates who:

Have resources

Can protect her and her children

Are a good parent

Are compatible.

Males are attracted to mates who:

Display signs of fertility

Question 9

A03

Answer 9

The logic of sexual selection – why have mechanisms for mate choice evolved?

After all choosiness requires time and energy.

It is because it pays to be choosy because the genetic quality of a mate will determine the genetic quality of the offspring.

Low quality mates (those who are unattractive and unhealthy) will be more likely toproduce unattractive, unhealthy offspring.

By joining forces with an attractive, high-quality mate, the offspring are higher quality and so the individual’s genes are much more likely to be passed on.

Question 10

A03 - SEX DIFFERENCES IN HUMAN MATE PREFERENCES. BUSS 1989

Answer 10

Study involving 10,000 people from 37 widely diverse cultures. The following was found;

• Women desired men with financial ambition
• Men were more concerned with physical attractiveness
  and mates who were younger than them. (Both potential cues of fertility and reproductive value)
• Both sexes desired intelligence, kindness and
  dependability

Question 11

A03 – SHORT-TERM MATING STRATEGIES

Answer 11

Clarke and Hatfield 1989 – Students on a college campus were approached by men and women experimenters who said:-

“Hi, I’ve been noticing you around campus and I find you very attractive”.

The students were then asked:

1. Would you go on a date with me?
2. Would you go back to my apartment with me?
3. Would you have sex with me?

Question 12

Clarke and Hatfield: Findings

Answer 12

Females – 50% agreed to go on a date

6% agreed to go back to his flat

0% agreed to have sex

Males - 50% agreed to go on a date

69% agreed to go back to her flat

75% agreed to have sex

These results gave been replicated in other studies and seem to provide
compelling evidence that men have evolved psychological mechanisms to ensure success in short-term mating – these include;

a) a desire for sexual variety,

b) the tendency to let little time elapse before seeking sex and

c) a willingness to consent to sex with strangers.

Question 13

SHORT-TERM MATING PREFERENCES

Answer 13

Men appear to have a number of evolutionary strategies with regard to sex, one of which has evolved for short-term mating success

The idea is that because men are competing for quantity of females in order to pass on more copies of their genes than a less successful rival, they would want to have sex earlier in a
relationship.

The less time a man waits before having sex , the larger the number of women he can impregnate in a given time.

Women however, are not under this evolutionary pressure as no matter how many men they have sex with, there can only have one pregnancy at a time.

Question 14

ISSUE – GENDER BIAS IN SORT-TERM MATING

Answer 14

But – It takes two to tango! Every time a man has sex with a willing partner the woman is also having sex with a new partner so men’s greater willingness to have sex with multiple partners could not have evolved without willing females.

Clearly there must be some benefits for women.

Greiling and Buss 2000, suggest that women profit in many ways, including using short-term mating as a way of leaving poor-quality relationships or as a way of producing more
genetically diverse offspring.

Question 15

LONG-TERM MATING PREFERENCES

Answer 15

Since parental investment is high in long-term mating, sexual selection would predict that both men and women would be choosy.

Poor long-term mate choice would mean wasted resources and opportunities.

Question 16

ACCORDING TO BUSS 2003 WOMAN WOULD BE ATTRACTED TO MALES WHO…

Answer 16

a) are able to invest resources in her and the children

b) are able to physically protect her and the children

c) show signs that they’ll be a good parent

d) are compatible enough to ensure minimal costs to

her and the children.

And what about the men?

Well in order not to give away resources indiscriminately, men would
be most attracted to females who display signs of fertility – an indication of their reproductive value.

The following research by Buss found universal trends in men and women .

Question 17

MALE PREFERENCES FOR YOUNGER WOMEN

Answer 17

One of the most striking conclusions of Buss’s study was that men have a distinct preference for younger women, which is a finding consistent with the theory of Sexual Selection because the younger the woman, the greater the fertility.

BUT Some critics have tried to explain this preference in terms of social power – Younger women are easier to control, and therefore are preferred as mates.

However Kenrick et al 1996 found that teenage males were most attracted to women who were 5 years older than them despite the fact that these women showed no interest in them and were clearly not
more easily controlled by adolescent males!

Question 18

PENTON-VOAK (1999)

Answer 18

Women prefer slightly feminized male facial shapes. Such faces are given positive personality attributions that might correlate with actual behaviour. In contrast, masculine features seem to signal immunological competence.

Women might be more attentive to phenotypic markers indicating immunological competence during the follicular phase of the menstrual cycle when conception is most likely.

Women’s preference for the odour of men with low fluctuating asymmetry increases with the probability of conception across the menstrual cycle.

Symmetrical men report more extra-pair copulation partners, and extra-pair copulation rates peak in
mid-cycle.

Female choice of a mate varies according to her stage in her cycle.

Woman chose a more feminine version of a male face as most attractive for a long-term relationship.

But during the high conception stage of her cycle the preferred shape of face was more masculinised.

Question 19

A03 - MATE-CHOICE IN REAL LIFE

Answer 19

Do studies such as Buss’s suffer from a lack of Validity?

• i.e. they may indicate preferences but they’re not a reflection of what happens in real life.

A study by Buss (1989) of actual marriages in 29 cultures backs it up.
This research confirms that men do choose younger women. Not only that, but men who divorce and remarry tend to marry women who are increasingly younger than they are.

Question 20

Reductionism

Answer 20

Ignores influences of social and cultural factors

E.g. social change means women need to be less resource orientated.

Theories that don’t take into account these influences are limited in their usefulness