3.1.4 - role of evolution and natural selection to explain behaviour including aggression Flashcards
what is evolution?
the gradual development of different kinds of living organisms from earlier forms during the history of the Earth
what is natural selection?
a gradual process by which heritable traits become more or less common in an environment
what is sexual selection?
when individuals successful in attracting a mate out-reproduce others in the population
how does natural selection occur eg. giraffes?
- giraffes were better adapted to their environment if they could reach foliage higher up a tree (main food source)
- a series of random mutations caused a variety of neck lengths to be present in the giraffe population
- giraffes with slightly longer necks had an advantage when searching for food
- these giraffes had a greater chance of reaching the reproductive age and were reproductively successful - they passed on their alleles to their offspring
- shorter-necked giraffes were unsuccessful at reproducing so their alleles died out
- sexual selection occurred over time meaning the frequency of alleles in the population changed
what is the environment of evolutionary adaptedness (EEA)?
the conditions in the environment that a species was adapting in response to at a particular time
what is a selection pressure?
part of the EEA causing a particular trait to be more favourable/advantageous in that environment
which EEA are evolutionary psychologists interested in?
the EEA when humans lived in hunter-gatherer groups
how can the EEA be used to prove that behaviour is the result of evolution?
in the EEA, humans best suited to their environment were the successful ones
fossil records are used to understand the EEA and therefore the type of behaviour which would be adaptive in it
once these behaviours are identified, they are matched to current universal human behaviours
this therefore argues that behaviour is due to brain structure and chemistry which developed and adapted over time
how does natural selection theory explain human aggression?
- in the EEA, the harsh nature of hunter-gatherer existence created a selection pressure for aggression
- individuals with aggressive genes were more able to defend themselves and compete for scarce resources like food, so had an advantage
- these individuals were more likely to survive, reproduce and pass on their aggressive genes - these genes proliferated in the population over time
what was the importance of selection pressures in the evolution of aggression by natural selection?
they would select genes coding for a moderate aggression level - if aggression increased continuously and became too high, this may be a disadvantage and limit the chance of survival
how might natural selection and the EEA have caused male aggression to evolve?
in the EEA, successful males were physically bigger and stronger, and psychologically more aggressive (better at hunting, able to defend threatened resources)
these successful males were more likely to be chosen by successful females to mate
therefore, masculine aggression is more physical and is likely driven by competition for mates
how might natural selection and the EEA have caused female aggression to evolve?
females have been more successful in the EEA if they were less physically aggressive - this would ensure they didn’t engage in conflict and hunting, thus protecting them and their children
Buss (1999) suggested females would still be competing for the best mates, but did this by belittling other females to potential mates so they appeared less attractive
therefore, female aggression is more emotional and verbal
strengths of the evolutionary explanation of aggression - brain structure and genes?
humans appear to have brain systems which produce and regulate aggression eg. the amygdala - these structure are found in other species too where they are involved in aggression (supports common descent - we have same ancestor)
the fact that male brains have evolved to have higher exposure to testosterone could indicate that this is why men are on average more aggressive than women (Mazur (1983) - inter-male fighting increased around puberty when there is a known rapid increase in testosterone)
there is apparent existence of genes which influence aggression (Brendgen et al. found significant evidence for genetic influence on physical aggression) - argue that genes wouldn’t have arisen in human genome if they didn’t have adaptive function in past
strengths of the evolutionary explanation of aggression - evidence of reasons for aggression?
theory states that aggression evolved to help individuals compete for resources like food
there is evidence that aggression in species increased when resources are scarce:
Allen et al. (2016) - correlated long-term environmental conditions with archaeological evidence from prehistoric graves, found that during famine or drought there was more evidence of violent death eg. sharp force trauma on bones
weaknesses of the evolutionary explanation of aggression - speculative?
relies on assumptions about EEA which can’t be tested empirically
risk that researchers will imagine EEA which fits their preconceptions and present this as fact
weaknesses of the evolutionary explanation of aggression - other theories of evolution?
aggression may have evolved in other ways like theory of sexual selection
human females may have selected mates based on aggression levels (more aggressive mate means offspring more likely to survive)
therefore, human males had to compete to be chosen, and those who mated had genes for higher levels of aggression
Puts et al. (2016) - human males more physically aggressive and on average larger/stronger than females
weaknesses of the evolutionary explanation of aggression - learning theory?
aggression may be learned rather than innate - especially as children exposed to aggressive behaviour appear more aggressive (Bandura et al. 1962 - children would imitate aggressive acts they’d witnessed an adult perform against an inflatable doll)
learning theory more significant than evolutionary theory in terms of reducing aggression - we can change what people learn but not their genes
issues and debates - reductionism?
idea argues that human behaviour can be reduced to evolutionary pressures from hundreds of thousands of years ago, and that other factors like social learning don’t impact complex behaviour
natural selection may influence human aggression but it is not the only factor - other factors include influences rom physical and psychosocial environment
issues and debates - determinism?
idea argues that we have little free will in whether we are aggressive or not because we are programmed by evolution to respond in an unchangeable way - could be used as an excuse or justification for socially unacceptable/aggressive behaviour
