Human reproductive behaviour

Human reproductive behaviour is an evolutionary approach as it tries to explain behaviour from the point of view of how it has evolved. Sexual selection is the process in which a species changes over time as a result of the passing on of the genes that make one individual more attractive than another. For example, evolutionary psychologists explain the relative hairlessness of humans in terms of sexual selection, as this trait was adaptive in that it enhanced reproductive fitness by indicating hygiene; it has evolved and developed over the centuries as it confers a net benefit.

There are two types of sexual selection: Intra-sexual selection is the competition within males as females are scarce resource for which males compete. Due to intra-sexual selection, men have evolved to have larger, more triangular backs which indicate strength and make them more attractive to females. Females on the other hand have evolved to have a typical hour-glass figure, which indicates health and fertility, making them attractive to male. Inter-sexual selection involves the apparent “choosiness” of females. Females invest highly in their offspring, and as a consequence, seek partners that can provide resources and protect them from predators. As a result of sexual selection, both males and females have evolved certain mate preferences which in turn, has lead to the evolution of certain physical characteristics.

Buss (1989) conducted a cross cultural study (37 cultures) using over 10,000 men and women. The data used to collect the data from the participants covered demographic information, e.g. age, gender, marital status etc. they also asked about preferences for variables such as marriage, age differences and characteristics in a mate. They found that women valued variables associated with gaining resources (e.g. money, safe environment etc), whereas men valued variables associated with reproductive capacity (e.g. youth, physical attractiveness etc).

We can conclude that historically women haven’t been able to provide for themselves so look for men who can. Men on the other hand have been limited to fertile women so have evolved to be attracted to women with a high likelihood of reproducing, so in essence younger women. Therefore most findings supported the idea that men and women differ consistently in the characteristics they find attractive in a potential mate. This shows evidence of intersexual selection as males and females look for different things in a potential mate.

There are some drawbacks with this study, e.g. the use of questionnaires. There’s always going to be social desirable answers as every individual wishes to comply with the social norms. Also the independent variable is one which cannot be controlled as it is naturally occurring so the only way to gain validity from this experiment is by applying the theory to the results making them unfalsifiable. Buss did not use a representative sample. In his study people living in rural areas were underrepresented as were those individuals who were less educated as the study relied on people completing a questionnaire.

In the case of homosexuality, Buss’s argument cannot account for homosexual relationships which clearly do not contribute to the survival of the species. Same sex relationships seem to have existed in most cultures throughout recorded history, so explanation for sexual selection cannot explain these relationships, therefore it cannot be generalised to all relationships. Buss’s survey of mate choice suffers from a serious problem of validity. The research has focused on preferences rather than on real life choices. For example, people may express a preference for an ideal partner (intelligent, kind etc.) but may have to settle for less. This therefore means that the study does not tell us about actual mate choice. However a study of real life marriages has conformed many of these predictions, such as, men do choose younger women (Buss).

In 1972, Trivers came up with the ‘Parental Investment Theory’ (PIT). This is an evolutionary theory which attempts to explain gender differences in reproductive behaviour. The PIT argues that differences in male and female reproductive behaviour are due to the amount of parental investments (PI) made by both sexes. Human males’ PI is relatively small. A man has a huge, indefinite amount of sperm and will remain fertile all his life, so therefore men can produce an infinite amount of children.

It doesn’t take that much time or effort to leave a woman pregnant so the best way for a man to maximise his reproductive success is to mate with as many women as possible. Women on the other hand have a very large PI. They have a limited amount of eggs and her reproductive life is shortened to about 30 years. As they only ovulate once a month, there is a limited amount of offspring they can have. Following conception she will have to carry the baby for 40 weeks, which will interfere with her heath and figure. Due to this, women have to be very careful when choosing a mate.

The relationship between sexual selection and human reproductive behaviour Natural selection suggests that successful animals evolve characteristics which enable them to out-perform rivals, increasing reproductive opportunities. Sexual selection is where individuals advertise both their own requirements in a mate and their …

Sexual selection is a process that favours individuals possessing features that make them attractive to members of the opposite sex or help them compete with members of the same sex for access to mates. Darwin believed that the competition between …

There are two consequences of anisogamy, intrasexual selection and intersexual selection. Intrasexual selection refers to the suggestion that males will compete amongst each other to mate with females. This results in some males proving their fitness and health over others, …

Darwins’ theory of natural selection suggested that all species were motivated by ensuring their survival. From this idea, came the concept of ‘survival’ of the fittest, through which only ‘adaptive’ traits and/or characteristics would be ‘naturally selected’. Darwin came to …

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