Biological Explanation 3: Natural Selection
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Evolution
What is evolution?
Evolution is the gradual development of different kinds of living organisms from earlier forms during the history of the earth. This means that all species share some genes with each other because they all have common ancestors.
Natural Selection
The process in which organisms better adapted to their environments are healthier, live longer and reproduce more frequently passing on the genes that made them reproductively fit their offspring.
For example, an animal such as a giraffe, that depends on foliage from trees as its main source of food would be better adapted to the environment, if they had the ability to reach more foilage higher up on the tree.
Genetic Mutation
Sexual Selection
There is a variety of neck lengths, caused by a series of random mutations. Every now and then a genetic mutation would occur causing a change in the organism, the giraffes that have slightly longer necks have an advantage over the shorter ones when searching for food, making them more likely to live to reproductive age.
Because they were reproductively successful, their allies were passed on, and because the shorter-necked giraffes were unsuccessful, their allies died out over time, the frequency of certain allies in a population changes.
Environment for evolutionary adaptation
The condition that prevailed in the environment at the time that the species was adapting in response too.
Why are females are less physically aggressive?
How does evolution explain aggression?
. In evolutionary terms success is measured by the production of offspring that survive to reproductive maturity. In the EEA, successful males were physically trigger and stronger and so would be those most capable of providing food and protecting their mates and offspring.
. Psychologically, males who were naturally more aggressive when their recourses were threatened pr when out hunting, would also have had an adaptive advantage. Such men might also have been prepared to attack other humans and take their resources in order to provide for their families.
. This gave males an advantage in terms of mate choice. Successful females chose mates who provide good genes, so big, strong men were favoured. Such men were also more likely to provide better resources in terms of food and protection, suggesting that those who displayed aggressive traits would be more successful than those who did not. Thus, competition for males has driven masculine aggression.
It would be an evolutionary disadvantage for females - who spend long periods of time pregnant, breastfeeding and looking after vulnerable young children in order to ensure their survival.
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Strengths
Weaknesses
Testable
Supporting Evidence
- Male brains do have minor differenced in structure compared to females, particularly due to a much higher exposure to testosterone before and after birth.
- Supporting research for aggression as an evolved solution to adaptive problems:
. Hill and Hurtado (1996) - found aggression leads to increase in social status in the Yanomamo tribe in Venezuela.
. Daly et al (1982) - found domestic abuse was used to dissuade romantic partners from infidelity.
. Shackelford et al (2005) - found use of mate retention strategies (female-directed violence) supported by studies of battered women.