Discuss the Relationship Between Sexual Selection and Human Reproductive Behaviour

Topics: Sexual selection, Physical attractiveness, Natural selection Pages: 6 (2152 words) Published: April 9, 2012
There are many theories that try to explain relationships between sexual selection and human reproductive behaviour. Evolutionary theory is one such theory. There are many different species in the world which, according to Darwin, all came from one source, e.g. a bacteria or organism. Within each species, natural variation occurs, therefore the individual beings within the specie look different from one another. These differences are caused by genetic makeup (50% from your mum, 50% from your dad). There are some genes like down-syndrome that get switched on when combined with other genes. Some genes can also undergo mutation- a random change (e.g. being born with six fingers, instead of five). Most mutations are harmful, for example Siamese twins joined by the brain, but some like the cheetah’s spots are good, they make it easier for the cat to camouflage better. This mutation increased survival fitness; therefore it got passed on and became a permanent feature. The other cheetah’s without spot started dying out, as they could not camouflage as well as the spotted one, and got caught when stalking their prey. Evolution is the process of natural selection according to Darwin; it enables us to find mutations which help us survive. In addition to natural selection, Darwin also suggested that species evolve through sexual selection. Darwin suggested that animals would evolve through time and end up with physical and behavioural characteristics that allow them to survive efficiently and compete effectively with rivals. For example, the peacock’s tail appears to reduce its chance of survival as it attracts predators and hinders its flight. But the tail is what helps it survive, as it attracts the females, the brighter, colourful and bigger the tail is; the more chance of mating it has. An example of sexual selection in humans is hairlessness. Although the loss of hair may have enabled us to keep cool in the hot weather by sweating, lack of hair meant we had to adapt to wear woolly clothes to keep warm during cold weather as we had no protection from it. Darwin explained that sexual selection compliments natural selection. If a certain characteristic becomes established as a universal preference among females, (e.g. square jaw lines, showing more masculinity) the males who possess the trait will have the best reproductive success. Intra-sexual selection involves men competing with each other for access to females. As a consequence of this, men have evolved larger, more triangular backs, as this indicates strength and makes the individual more attractive to females. Sexual dimorphism refers to the different characteristics that females and males have. This can be explained via natural selection- certain characteristics lead to greater chances of survival, therefore increasing reproduction. Pagel and Bodmer proposed that hairlessness was a way to advertise their skin (e.g. having healthy skin/ no parasites), therefore more sexually attractive. The trait therefore became desirable in a mate; the greater loss of body hair in women would have resulted from stronger sexual selection pressure. This proposes why males care more about attractiveness whilst females favour resources. Reproductive behaviour shows that differences between male and female behaviour arise because of different values of sperm and egg. Males tend to be more forward when it comes to trying to have sex with a woman whilst showing off, whereas women are more picky and coy, wanting to choose the right man. This is not just a western trait but global. Men can provide about 110 million sperm at one time, whereas a woman can only produce one egg a month. The value of sperm is considerably lower compared to a women’s egg. Males cannot be sure of paternity as a women can, as the child grows inside her, she is 100% certain the child is hers. Whereas males may think the baby is not theirs as they have no actual proof. Natural selection favours multiple pregnancies and...
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