Through our discussions in class and our readings, we currently believe that the reason for monogamous relationships in mammals is directly related to parental care. It is advantageous for mammals, which are K selectors that produce few offspring that take longer to fully mature, to have monogamous parents that can work together to provide for these offspring. However, both articles provide a different reason for monogamy in mammals.
Opie, Atkinson, Dunbar, and Shultz state in their article that they believe that monogamy evolved as a way to combat infanticide. Their evidence for this comes from their conclusion that male infanticide is the only trait that “precedes the initial shift to social monogamy.” Their research has lead them to conclude that paternal care evolves after monogamy, and therefore cannot be the primary reason for monogamy in mammals. Lukas and Clutton-Brock, however, assert that male infanticide is typically found in species where lactation exceeds the duration of gestation, and there is no difference of significant consequence to justify this being the reason.
Clutton-Brock and Lukas state a different reason – monogamy has developed as a result of breeding females being intolerant of each other, and males are unable to defend more than one. They assert that social monogamy evolves when female density is low and they are uncooperative, and so males would be stretched too thin over their territory guarding multiple.
I believe that Opie, Atkinson, Dunbar, and Shultz had a more convincing argument. Compared to Lukas and Clutton-Brock, they examined many more reasons with a variety of methods, including phylogeny, primate trait data, and analyzed ancestral states and correlated evolution between monogamy and other traits. To me, it felt as though Lukas and Clutton-Brock were too quick to dismiss other theories, and did not go into sufficient depth to explain why, such as in their analysis of male infanticide.
These articles have changed my understanding, because they both discuss a variety of possible explanations that I did not consider during class or from my readings. Parental care was discussed as having evolved after social monogamy, which was a surprising revelation. Meanwhile, the other explanations made sense, and forced me to consider new reasons for social monogamy in mammals.