We had previously thought that monogamous relationships were due to the offspring requiring greater parental care than just one parent could provide. The female of a species is more likely to provide parental care than the male because it is certain that the eggs laid contain the mother’s genes, but they may have been fathered by another male. It is different when there is external fertilization and both the father and mother are able to be confident the genes the offspring possesses are a combination of their own. However, both articles suggest different reasons for how social monogamy could have occurred in various species.
The article “The Evolution of Social Monogamy in Mammals” by D. Lukas et al suggests monogamy has been created from a state in which females are solitary and the males range overlap between several females. When the family groups became less stable, caused by intense competition between females who were intolerant of each other, it created a low density of females. Due to these conditions the males were able to mate with the remaining female in their territory range, and only that female. Any paternal care was promoted by the behaviors of social monogamy.
According to the article written by Opie, et al, Social monogamy may arise when the risks of male infanticide are high especially when the female of the species is suckling two infants of different ages at the same time. While the female is not releasing eggs because she is nursing an infant a male who is not the father may kill the infant to make the female able to reproduce again faster. Gerbils, a common household pet, are a good example of this phenomenon; they will attack infants that may not be theirs to allow the female reproduce sooner. Social monogamy would allow the male to protect the female from other males; therefore, increasing the offspring’s likelihood to survive.
I believe the article by Opie, Atkinson, Dunbar and Shultz makes a more convincing scientific argument to support socially monogamous relationships within animal species. As stated in the article, “of the traits tested, high male infanticide alone consistently preceded the appearance of social monogamy across primates. Social monogamy can reduce the incidence of infanticide…” There is a clear cause and effect component to these results that cannot be ignored. The methodology and data analysis of the article written by Opie et al was definitely easier to follow and had more of a direct correlation to focus of the study, infanticide in males.
The article written by Opie et al, definitely explained why infanticide was so common among males of the same species. I remember learning about this phenomenon when I was younger and I could not think of an evolutionary advantage to killing your offspring. Now I realize that it is because the male may not be able to be confident that a child has his genes and would like to have the female be ovulating as soon as possible. These articles have further reinforced the idea that social monogamy is an anomaly not a normal occurrence; far more species are not monogamous and it is the human species that is unusual.