Explain, with examples, how the processes of natural selection and sexual selection are thought to have contributed to modern-day human behaviour

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Explain, with examples, how the processes of natural selection and sexual selection are thought to have contributed to modern-day human behaviour

Human physical and psychological mechanisms are subject to an environment which is ever changing.  Selection enables us to develop and so cope with these random changes by selecting the mechanisms which enable us to cope with these external factors and thus making them much more likely to be inherited by our next generation (Clegg, 2007).  It is the survival of the gene to which selection refers to as opposed to the species, for example, the gene which enables the individual to reproduce effectively or the gene that predisposition certain behaviours which are most suitable to it’s environment will be passed down to future generations.  This means that genes that are less effective for survival or reproduction are less likely to be inherited (Barrett et al., 2002 as cited in Clegg, 2007 p121)  

It is common practice to divide selection into two process: natural selection; and sexual selection (Clegg, 2007).  Natural selection refers to the process of genes which are responsible for physical and behavioural characteristics and are most suitable for survival, being inherited by the next generation.  Sexual selection (which could also be argued as being a sub-process of natural selection) refers to the process of genes which influence the physical and behavioural characteristics of an individual that subsequently enables reproductive success, being passed down to the succeeding generation.

One phrase which is used in conjunction with natural selection is ‘survival of the fittest’ (Clegg, 2007).  An example why could be; an individual possessing a behavioural trait which enabled him to survive the most effectively in his environment.  This would give him the probability of a longer lifespan than his counterparts and so potentially more time to reproduce and therefore pass on that particular behavioural trait to his offspring.  Hence the phrase ‘survival of the fittest’ as addressing the reproductive success of a gene or the ability to pass on copies of this gene as opposed to the physical interpretation of the word ‘fittest’.  

Studies on adaptations of an evolved property or trait can be seen as an essential part of research into how selection processes have influenced modern-day behaviour.  An example of this which has been a topic of media interest in the past few years is the subject of obesity.  Western culture in particular in this day and age involves a high intake of fatty and sugary foods.  This can be explained by the survival behaviours in our ancestors, which made them crave foods with high calorific content as food was generally scarce.  This would mean that they would receive the highest amount of nutrition available to them.  This has seemed to have contributed to the lifestyle of modern-day humans.  But as this trait can lead to obesity, in this day in age it is actually damaging to reproductive success.  (Riley, 2005 as cited in Clegg, 2007).  This example could also highlight the concept that there is a significant delay in the evolution of an adaptive mechanism to problems the human race faces.  

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Altruistic behaviour can also be seen in modern-day humans and is linked to natural selection (Clegg, 2007) .  Altruism can be described as an act a person undertakes which benefits another individual at a cost to the person performing that act.  This however, means that by performing an altruistic act on a close family member who is likely to share your genes, especially an act which helps them survive to a reproductive age, you are more likely to aid the successful inheritance of that gene in future generations (Clegg, 2007)  Altruism is believed to be adaptive (Clegg, 2007).


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