Evolution, natural selection and aggression

Question 1

Evolution by natural selection

Genetic differences between organisms create variation

Answer 1

Variation arises because genes from parents are combined and also due to spontaneous mutations (changes) in genes

Small differences between individuals don’t matter when resources are available, but when life is hard, individuals who possess characteristics that help them survive and successfully reproduce pass genes on to the next generation. Individuals who fail to reproduce are not represented in future generations

Reproduction is key - If an individual doesn’t reproduce successfully the new characteristics are not passed on

Question 2

The process of natural selection

The environment ‘chooses’ individuals who can survive and reproduce successfully

Answer 2

After many generations of small differences, there are individual who are different from their predecessors. This occurs by natural selection (Darwin). This is often called ‘survival of the fittest, ‘fittest’ referring to the characteristics that best match or ‘fit’ the demands for the environment

Natural selection is due to the survival of genes and happens when there is competition for scarce resources (including reproductive mates). The most useful genes (those that aid survival and reproduction) are kept 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 predecessors

Question 3

Sexual selection

The influence of evolution acting on the success of reproduction

Answer 3

Sexual selection explains why some characteristics that appear disadvantages actually confer an advantage- because the characteristics are attractive to potential mates

For example, the peacocks tail appears to threaten the male birds survival but the advantage for the male is that his tail is attractive to females ( a sign of his genetic fitness, he carries the burden but still manages to survive)

Some characteristics (especially behaviours) are adaptive because they provide an advantage over competitors for reproductive rights, 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) and the genes that gave rise to the characteristics remain in the population

Question 4

Evolution and aggression

Protecting yourself , partner and offspring would have enhanced survival and reproduction

Answer 4

Guarding your partner - mate retention strategies are aggressive behaviours men use to keep partners and prevent them ‘straying’. Direct guarding is male vigilance over partners behaviour, e.g. coming home from work early (Wilson and daly)

Guarding your offspring - human parents direct aggressive acts towards other people (or animals) who threaten their children. Aggression protects parents ‘investment’ and is one of the very few situation in which females behave as aggressively as males

Question 5

A strength is evolutionary theory can explain gender differences in aggression

Answer 5

Cooperative females are likely to be naturally selected because cooperation protects them and their offspring as a group (so reduced aggression is selected in females)

In contrast aggressive males are more likely to be naturally selected because they make better hunters (evidence from studies of chimpanzees e.g. Manson and Wrangham)

This supports the explanations for gender differences in aggression, and increases the validity of theory of natural selection

Question 6

Competing argument

Answer 6

Any evolutionary explanation is uncertain because it is impossible to test evolution directly, which is why most research is correlational

Because variables are just measured and not manipulated, correlational research can never rule out the effects of other factors on aggressive behaviour. So this method does not allow us to draw cause-and-effect conclusions

Question 7

A weakness is evolutionary theory cannot explain cultural differences

Answer 7

For example, amongst the Kung San people of the Kalahari in Southern Africa, aggression is discouraged from childhood and is therefore rare

In contrast the Yanomami of Venezuela and Brazil have been described as ‘the fierce people’, and aggression is an accpted behaviour to gain status in their structured society (Wolfgang and Ferracuti)

Therefore, aggression is not universal, which suggests innately determines behaviour can be outweighed by cultural norms

Question 8

Application: Evolutionary theory helps us understand human relationships

Answer 8

(Buss) Found in 33 countries that males preferred younger, more attractive and chaste women (this enhances their reproductive success because women are more likely to be fertile)

Females preferred older, wealthier and ambitious or hard-working men (likely to increase their reproductive success because there children are well-supported)

This supports evolutionary theory because It shows that the predictions from the theory are upheld by evidence

Question 9

Issues and debates

the use of fossils as evidence illustrates psychology as a science

Answer 9

Ladeveze et al reported a fossil find of extinct marsupials which showed that the males were much bigger than the females

This reveals male-male competition as bigger males has an advantage in aggressive competition for reproductive rights (more likely to be reproductively successful, passing on genes that made them bigger to the next generation of males

This shows how an objective scientific approach can be used to study the evolution of aggressive behaviour