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Outline and evaluate evolutionary explanations of parental investment

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Charley McCarthy Highsted School Assignment 4 Outline and evaluate evolutionary explanations of parental investment (24 marks) The evolutionary explanations of parental investment all believe that parents invest in their offspring in various ways, such as giving food and the energy put into rearing the child, and risks taken to protect them. This investment is defined as 'any investment made by a parent in one of his or her offspring that increases the chance that the offspring will survive at the expense of the parent's ability to invest in any other offspring (alive or yet to be born)' by Trivers, 1972. The amount of parental investment however, differs between males and females. Trivers, in 1972, came up with the parental investment theory. Central to this is the fact that men and women do not usually invest the same amount in their offspring. Women have to invest more to start with, as women have far less eggs, and these are harder to produce, than men do sperm. As well as this, females are limited to how many offspring they can have, whilst males can produce a virtually unlimited number. ...read more.


This shows why attractiveness of females is so important to male humans in comparison with males of other species. Despite this theory explaining why it is shown that usually women select the mate, and males compete to be it, this is not always the case. For example, after WW2, when there were fewer males left than females, there was a baby boom, leading to the 1960s having more marriageable women than men available, which may explain the change in sexual morals (greater female competition meant a society more dominated by male mating strategies) or could have been due to the introduction of the Pill. This is supported by a study by Hill and Hurtado, (1996) who found when they studied two Indian cultures in South America, that although they both lived in very similar environments, the Hiwi had more men so had stable marital life, whereas in the Ache, there were more women and extramarital affairs were common, showing that sexual morality decreases when the ratio of women is higher to that of men. This theory is credible, because it allows a way of explaining the link between sexual selection, mating behaviour and parental investment (Buss, 1998), and shows that when mating, men gain from polygyny and women monogamy. ...read more.


This causes more nutritious blood to travel to the foetus, benefiting it at the expense of the women carry it (Haig, 1998). It has been found though, that those mothers who have higher blood pressure through their pregnancy are less likely to suffer from spontaneous abortion (Haig, 1993) and tend to have larger babies (Xiong et al. 1993) suggesting it is an adaptive strategy to produce healthier babies. After birth, the conflict continues. Natural selection causes parents to maximise fitness by investing in their current offspring, decreasing this investment in favour of younger offspring as they grow up. Resources are given more to younger children as these have a higher chance of dying before they reach adulthood than the older children do. This causes conflict, as the children want the parent's main focus to remain on them for as long as possible. In comparison, it has been suggested by Salmon and Daly (1998) that younger children do not bother to compete with siblings for parental attention, instead acting cooperatively, so as to form alliances with non-kin. A contrasting non-evolutionary theory argues that younger children tend to be more co-operative because they learn to negotiate through coping with older siblings (Shaffer, 1993). ...read more.

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Although the writer has outlined the explanation of parental investment a lot of the work is not in the writer's own words. Also to evaluate the subject there would have to be consideration of its weaknesses and strengths.

References have been used and the writer has clearly read around the subject More work is needed on summarising what has been read and putting this into the writer's own words.

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Marked by teacher Linda Penn 01/05/2013

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