Evolution and aggression

- Evolution happens because genetic differences between organisms createvariation. Such variation arises because genes from parents are
combined and also due to spontaneous mutations in genes.
- those individuals who possess characteristics that help them when
to stay alive and reproduce are the ones who pass their genes on to the
next generation. Individuals who cannot survive or fail to reproduce are not represented in future generations.
- individuals who can survive and reproduce successfully.

- Natural selection happens when there is competition for scarce
resources (including reproductive mates).
- The genes which are most useful (because they produce characteristics which aid survival and reproduction) are retained in the population and over time become more frequent.
- The outcome of selection is adaptation - the survivors are better suited to life in the current environment than the predecessors,

- The influence of evolution acting on the success of reproduction (rather than survival) is called sexual selection. Sexual selection explains why some characteristics that might appear disadvantageous actually confer a survival advantage because the characteristics are attractive to potential mates.
- Other characteristics (especially behavioural ones) are adaptive because they provide an advantage over competitors for reproductive rights.
- For example, it pays for a male to be aggressive because it allows him to fend off potential reproductive rivals.
- The aggressive characteristics that allowed the animal to reproduce in the first place are passed on to offspring if they are genetically-determined

- In human evolution, being able to protect yourself and your possessions (including partner and offspring) would all have enhanced survival and reproduction so would have been modified by natural selection.
- Mate retention strategies are the often aggressive behaviours men use to retain their partners and prevent them from 'straying"
- According to Margo Wilson and Martin Daly (1996) direct guarding involves male vigilance over a partner's behaviour, for example checking who they've been
seeing, coming home from work early, etc.
- Guarding your offspring example - human parents will direct aggressive acts against other people (or animals) that threaten their children. - This aggression
is adaptive because each child is a valuable genetic commodity.
- Aggression is a way for parents to protect their 'investment", increasing the offsprings reproductive chances later in life.
- Eric Steiner (2016) points out that protecting offspring is one of the very few situations in which females behave just as aggressively as males.

- A strength of evolutionary theory is that it can explain why males are more aggressive than females.
- Females who are cooperative are likely to be naturally selected because cooperation helps them protect themselves and their offspring as a group.
- Therefore, reduced aggression is selected in females. In contrast males who are aggressive are more likely to be naturally selected because they make netter hunters.
- Evidence from studies of chimpanzees supports this pattern of
gender diferences (e-g. Manson and Wrangham 1991).
- This is a strength because it explains gender differences in aggression today, and increases the validity of the theory.

- However, any evolutionary explanation is uncertain
because it is impossible to test evolution directly.
- This is why most research
is correlational, for example finding associations between mate retention
behaviours and aggression. This method does not allow us to draw cause and-effect conclusions.
- Because variables are just measured and not manipulated, correlational research can never rule out the effects of other factors on aggressive behaviour.

- A weakness in evolutionary theory is there are differences between cultures in aggressive behaviour.
- For example, amongst the !Kung San people of the Kalahari aggression is discouraged from childhood and is therefore rare.
- In contrast the Yanomami of
Venezuela and Brazil have been described as 'the fierce people' - aggression appears to be an accepted behaviour to gain status in their structured society (Wolfgang and Ferracuti 1967).
- These differences in aggression are not universal and suggest that innately determined behaviour can be outweighed by cultural norms.

- Evolutionary theory can help us understand human relationships as it predicts that we should choose partners who will enhance our reproductive success.
- David Buss (1989) found that, across 33 countries, males preferred younger, more attractive and chaste women, presumably because this enhances their reproductive success because such women are more likely to be fertile.
- Females preferred older, wealthier and ambitious or hard-working men, which is likely to enhance their reproductive success because their children are well-supported.
- This supports evolutionary theory because it shows that the predictions from theory are upheld by evidence