Thursday, April 1, 2010
Breaking the rules of sex
In the ecology unit, the sexual relationships between organisms of a species were discussed. Some species practice polygamy, having multiple mates, while other species practice monogamy, having only one mate. However, Jerry Coyne has mentioned instances where monogamy has rather become "social monogamy" (159) not actual monogamy. For example, Coyne brings up the example of the Australian fairy wren of which, during mating times, species mate with others "more often than they do with their 'social mate' " (159). What are other examples of species that practice this type of "monogamy," and what could be the selective advantage to this sort of relationship?
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When we look at "social monogamy", there are many examples that demonstrate this concept. As you've noted, Coyne brings up the fairy wren of Australia. While bringing this up, he takes particular notice of the fact that although the wrens are "monogamous", they display "striking sexual dimorphism in plumage" - a characteristic that is much more useful and prevalent in polygamous relationships (159). Now, there are many examples of organisms just like the fairy wren. For instance, animals known for their "monogamy" such as the gibbon or the swan, are actually socially monogamous - not completely monogamous. In otherwords, they engage in what humans call "cheating".
ReplyDeleteAfter saying that, it can be inferred that for humans are also socially monogamous (sometimes). Although humans declare faithfulness to one mate; in reality, adultery is common and social monogamy is the norm. In fact, "strict monogamy is almost inexistent, as creatures that do pair for life, occasionally have flings on the side"(http://news.softpedia.com/news/Monogamy-is-an-Oddity-42006.shtml). Furthermore, 90% of all birds are socially monogamous as Coyne states in the section "Breaking the Rules".
But why is that? Well, Staying faithful is extremely hard for animals, as the males are programmed to spread their genes and females to get the best genes from the best males for their young. Thus, being socially monogamous as opposed to strictly monogamous is actually a selective advantage. Males are able to mate with more females, thereby spreading their genes, speeding up the rate of natural selection and creating healthier, stronger offspring. Consequently, females are able to choose more males that have appealing characteristics - characteristics that are selective advantages in the environment in order to pass on to the offspring. Finally, this relates to the theme of continuity and change. With social monogamy, changes in the gene pool speed up due to a faster rate of natural selection for fit genotypes.
Connie referred to social monogamy as “cheating” (Lu, 2010), but is social monogamy really cheating? While male fairy wrens are indeed mating with other females, Coyne points out that “females mate with other males more often than they do with their ‘social mate’ ” (2009, p. 159). In other words, adultery among fairy wrens is bilateral and commonplace; both males and females engage in extra-pair mating, and, unlike adultery among humans, extra-pair mating among fairy wrens is considered to be the norm. I believe that the difference between how fairy wrens view adultery and how humans view adultery implies that there is also a difference between the relationship between a fairy wren social pair and the relationship between a human social pair. While the human institution of marriage is, in most cultures of which I know, meant to permanently bind two individuals in the bearing of offspring, raising of offspring and breadwinning, the fairy wren institution of social pairs is only meant to bind two individuals in, perhaps, raising of offspring and breadwinning, and not in the bearing of offspring. Therefore, just as there is nothing wrong with a married man watching a movie with a female friend because watching movies is not an activity reserved for mates, there is nothing wrong with a female fairy wren mating with an extra-mate male fairy wren because mating, among fairy wrens, is not an activity associated with mates.
ReplyDeleteAs Connie stated, most bird species are socially monogamous. More examples include the eastern bluebird and the white ibis (Barash).
Several centuries or millenia ago, polygamy among humans was not rare, especially among the priveleged (such as heads of state), who maintained harems of concubines or had affairs at his whim. True sexual monogamy is only a recent development in human history, perhaps a product of human emotion. Social monogamy is advantageous in that it allows more offspring to be produced within a species while at the same time maintaining allowing every two individuals to share the tasks of breadwinning and raising children.