Most modern human cultures are monogamous, where one male mates with one female. In chapter 6, "How Sex Drives Evolution," Jerry Coyne explains that dimorphism, the difference in appearance between males and females, tends to point toward a more polygamous mating system.
Relate human dimorphism, or lack thereof, to our mating system. What are the evolutionary advantages to monogamy (or polygamy) in human society?
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In examining dimorphism, it seems at first that this is a selective disadvantage. As Coyne points out, the elaborate displays and characteristics of the male not only draw unnecessary attention to the organism, but also expend a lot of energy. However, due to sexual selection, as explained by Darwin, this selection increases an individual's chance of acquiring a mate. Thus, in the long run, dimorphism is a good thing.
ReplyDeleteConclusively, it appears that dimorphism is wasted in monogamous species such as humans. According to Campbell, there are different types of relationships. One is monogamy - seen in humans - where one male mates with one female. Another is polygamy, in which one male mates with multiple females (Campbell 1134). Elaborate ornamentation or rituals for the males seems unnecessary for monogamous relationships and thus point to a selective advantage for polygamous relationships. In fact, Coyne makes the point that many species are merely "socially monogamous but not actually monogamous" (159).
However, with regards to humans, it appears that humans have less sexual dimorphism than say, the fairy wren of Australia. If humans are in a monogamous relationship, there is no sexual competition and no sexual selection. Extreme dimorphisms point to polygamy as selectively advantageous - due to increased capabilities of reproduction. However, with the minimized dimorphism seen in humans, it is more selectively advantageous to have a engage in monogamy. This way, because there is no elaborate ornamentation in the males, the males didn't expend more energy to gain more mates. This would ultimately lead to increased ability to survive and reproduce.
Finally, this relates to the theme of evolution naturally. A species has either developed or failed to develop dimorphism, which in turn leads to predominantly polygamous or predominantly monogamous characterstics - depending on which is the selective advantage.