I believe the reason for monogamous relationships in mammals is that it increases the viability of the offspring to have the protection of both parents. In monogamous relationship, the male is likely to stay with his mate because there is a higher chance for his genes to be passed on and survive if he were to protect the offspring of one mate rather than inseminating many females.
In The Evolution of Social Monogamy in Mammals, D. Lukas determines that social monogamy evolves in species where breeding females are intolerant of each other and female density is low. In a comparison between Primates and Carnivora, where there is a high incidence of social monogamy, and herbivorous order, the results suggest that the “evolution of low range-overlap and social monogamy may be a consequence of a reliance on resources of high nutritional value but low abundance.” This explains why breeding females are intolerant of each other since the resources they have are limited and can affect the viability of their offspring if they do not get enough food. Social monogamy allows the offspring to have enough food since both parents are foraging for food. According to Figure 1, the estimated probability of social monogamy is higher at lower population densities. Also, since the ancestors of monogamous mammalians were usually solitary meaning that the females foraged independently, this made it harder for males to mate more frequently at lower population densities if the females were so far apart.
In Male Infanticide leads to social monogamy in primates, Christopher Opie determines the cause of social monogamy to be male infanticide. According to Opie, social monogamy evolved from polygyny when there is high infanticide. Social monogamy reduces the instance of male infanticide because it enables a shorter lactation period compared with gestation. Also, social monogamy reduces the risk of infanticide because both parents can defend the infants instead of the offspring’s care falling entirely on the mother. Opie determines that male infanticide is the only factor that precedes the shift from polygyny to social monogamy whereas the other factors came as a result of social monogamy.
I believe that the article, The Evolution of Social Monogamy in Mammals makes a more convincing scientific argument because if the offspring requires more food than one parent can supply, a male could increase his reproductive success by helping to care for his offspring rather than going off to search for more mates. Lukas suggests that a reason for the evolution of social monogamy can be due to the less abundant, nutritional food of primates that results in the need for more than one parent to help supply food to the offspring. The article also states that although male infanticide is lower in socially monogamous species, there is no direct association between both instances and the evolution of both traits seems to have occurred independently of each other. Also, Opie’s article also states that high infanticide rate do not always correlate to the species evolving to become socially monogamous and that other factors such as the environment play a big role in determining the social system of the species.
These articles have changed my understanding of monogamy in primates because I never knew of all the possibilities of why social monogamy can evolve in primates such as male infanticide or how the distance between females plays an impact as well. The most surprising aspect of what I read was how evolution played such a big role in finding out what social system the ancestors of social monogamous mammalians were of and how these results varied across both experiments depending on the method used.