Social monogamy can be beneficial for a few reasons. First, it ensures that both the male and female have a mate. In solitary living and group living, males are not guaranteed an opportunity to reproduce and pass on their genes. Social monogamy, however, allows for each gender to have a consistent opportunity to mate. Social monogamy also reduces competition between males of the same species in the long run, as there is no discrepancy over who mates with who, and no need to show dominance every mating season. Social monogamy can also lead to paternal care, which would increase the viability of offspring and their likelihood to reproduce as well.
The article by Clutton-Brock et. al suggests that social monogamy developed due to competition between females and the distribution of individuals. Clutton-Brock et. al provide evidence for social monogamy developing most often in areas of low population density, where it would be more beneficial for a male to stay with one female than go searching for a new mate every breeding season. It is also suggested that social monogamy develops in areas where females compete with each other and therefore cannot live in close proximity to each other, making it more beneficial for males to choose one mate.
The article by Shultz et. al provides evidence for male infanticide being the most likely cause of social monogamy. While Shultz et. al reference similar theories on the development of social monogamy as Clutton-Brock et. al, a different conclusion is made. It is suggested that the need for paternal care is strongly correlated with social monogamy. Male infanticide occurs most often in species with long lactation periods, mainly because killing the offspring of a female who may spend a very long time nursing allows for a new male to reproduce with her sooner. However, social monogamy leads to shorter lactation periods, and because of this there is less male infanticide.
While I found the article by Shultz et. al a much easier read, I believe that the article by Clutton-Brock et. al was more reliable due to the amount and type of data provided. Clutton-Brock et. al included a lot of observable data and had a fairly large sample size of 2545 mammalian species, while Shultz et. al seemed to mainly rely on a few statistical tests and focused less of the article on scientific observations. Before reading these articles I understood very little about social monogamy in non-human mammals. While both articles suggest different primary reasons for the development of social monogamy in primates, they each acknowledge the same possible hypotheses. What surprised me the most was that social monogamy may have developed not for the purpose of parental care, but instead for the convenience of males who cannot cover enough territory to consistently mate with multiple females. The idea that population density influences the need for social monogamy was new to me, and I found the concept of it both logical and fascinating.