The evolution of human behaviour

Question 1

1. Why differences between the sexes? Two explanations… what are they

Answer 1

Ultimate vs. proximate causation

Question 2

1.1 Ultimate causes –» sex theory

Answer 2

Sex differences theory in humans​:

Females produce exactly one half of the gametes that produce offspring: so do males​

Mean reproductive success is the same for males and females (ignoring small differences when the sex ratio deviates from 50:50)​

Question 3

Why is intrasexual competition more intense in men?

Answer 3

Psychologist Martin Daly: ​

1) Darwinian reproduction = matter of differential reproduction among same sex competition.​
- Male fitness more variable and rank-dependent.
- Successful men have higher fitness than any woman​
- Men are likelier to die without reproduction​
- Men have evolved to compete with one another and are less deterred by danger.

Question 4

Winston Blackmore: Bountiful, British Columbia

Answer 4

Blackmore is the leader of a polygamist Mormon group. As of 2016, he had fathered 145 children.

Question 5

Males have a higher reproductive ceiling… what does this mean.

Answer 5

Human males have a higher potential ceiling than females: it also means that males are more likely to die without reproducing than females​

This leads to higher reproductive variance in males

Question 6

Why does unequal reproductive variance matter?

Answer 6

Men are willing to take greater risks

Question 7

Risk taking behaviour

Answer 7

Men are more likely to kill and be killed

Question 8

According to Martin Daly and Margo Wilson, there are two important contexts for murder

Answer 8

1) Social competition: a challenge to social status​

2) Material competition: robbery; business rivalry

Question 9

Risk taking behaviour appears linked to income…

Answer 9

to income inequality

Question 10

Discounting the future​

Answer 10

Evolutionary psychologists have shown that people often discount the future when it comes to resource use​

Most of us tend to spend what we have now instead of setting some aside for future use​

This abstract idea has dramatic consequences in the real world

Question 11

FIG 14.26 Homicide rates are highly correlated with male life expectancy.

Answer 11

These data came from neighborhoods in Chicago in which males could expect to live anywhere from less than 55 to more than 75 years after the effects of homicides themselves on life expectancy are removed.

Question 12

1.2 Proximate causes

Answer 12

Genes, hormones, socialization and learning

Question 13

Sex determining region of Y (SRY)

Answer 13

SRY gene (=testis determining factor, TDF) acts as a developmental switch triggering the development of male characteristics: its effects in humans start at 6-8 weeks of gestation​

It upregulates transcription factors that upregulate male gonadal development and the production of testosterone​

This influences, among other things, brain development

Question 14

Sex differences in mammalian brains

Answer 14

Sex differences in mammalian brains arise from underlying genetic differences and gonadal hormone exposure ​

Recent work on mouse brains showed that exposure to prenatal androgens induced sex-specific gene expression causing 2854 and 792 transcripts to become differentially expressed on XX and XY genetic backgrounds

Question 15

Are there male and female brains?

Answer 15

This has been the subject of recent controversy​

1) Joel–» no such thing as a ‘male’ brain and a ‘female’ brain: they argue that there is extensive overlap in brain structure across the sexes​
2) Using a large sample (MRI scans of 1566 individuals) Chekroud et al. (2016: PNAS USA) found that multivariate analyses of whole-brain patterns (morphometry) can reliably discriminate sex in 93% of cases.

Question 16

Do the sexes differ in height and weight?

Answer 16

1) The univariate analysis of height did not result in a clear separation of the sexes
2) BUT a bivariate analysis (plotting height vs. weight) increases the separation: the sexes begin to fall into two groups