Monogamous relationships are most prevalent in situations in which the offspring requires the protection and care from both the mother and the father. It is advantageous for these species because it increases the survivability of their offspring and therefore, their genes can be passed on to future generations.
According to a study conducted by Christopher Opie, Quentin D. Atkinson, Robin I. M. Dunbar, and Susanne Shultz, the cause of social monogamy in primates is male infanticide. The scientists arrived at this conclusion by testing three different hypotheses to discover how each correlated with monogamous relationships. They found that although all three were related to this phenomenon, biparental care and female range overlap are only consequences of monogamous relationships among primates. The only factor which preceded monogamy was male infanticide. Their reasoning is that as infanticide rates drop, both parents are needed to defend the young offspring.
However, based upon the research of D. Likas and T.H. Clutton-Brock, male infanticide is “unlikely to be the principal mechanism for the evolution of social monogamy in mammals”. Instead, they suggest that social monogamy has evolved from solidarity living where females have a very low population density. Because males are unable to defend such a large territory, they must resort to monogamous relationships.
After reading these two articles, I believe that “The Evolution of Social Monogamy in Mammals” by Lukas and Clutton-Brock has a more persuasive argument. Although the PNAS article had substantial evidence, they did not explore the different hypotheses to the extent that the Science Magazine article did. For example, the PNAS article only approached their research from one perspective, while the article done by Likas and Clutton-Brock discussed population density, body mass, home-range size, and diet to support their conclusion. Likas and Clutton-Brock also explained all conflicting information and data in their discussion section. One example of this is their explanation on how some primates have evolved to become socially monogamous despite having ancestors who were living in groups.
Reading these articles has not necessarily changed my understanding of social monogamy in primates, but it has definitely enriched what I had already learned. I had previously known that in order for monogamy to have become a stable mating pattern, it must have been an evolutionary adaptation. Now I understand why it is advantageous for an organism to have two parental care units, and I am more familiar with the phylogenetic history of socially monogamous species. One of the most shocking facts I read was that 41% of males in socially monogamous relationships do not show parental care to their offspring. I initially believed that if a species had monogamous practices, then parental care must also be there by default.