Social monogamy is a rare occurrence in nature, but especially within the mammals, where less than 3% of species are monogamous. These monogamous species could have evolved a pair formation to either defend each other and potential offspring from predators or to assist each other in parental care and reduce the resource usage on any single parent. In order for the shift to monogamy to be successful, the benefit of protecting and providing for offspring must outweigh the missed opportunities of further mating.
While the costs and benefits of transitioning to monogamy within the mammals are known, the mechanism for the shift is still debatable. In their article, “Male Infanticide leads to social monogamy in primates,” Opie, Atkinson, Dunbar, and Shultz argue that the pressure of infanticide by rival males pushed for social monogamy in order to protect the offspring, stating that “our analyses suggest that socially monogamous species are much more likely to have low male infanticide rates, presumably as social monogamy provides an effective counter-strategy.” In contrast, Lukas and Clutton-Brock argue in their article, “The Evolution of Social Monogamy in Mammals,” that social monogamy is caused by the need to defend the female from rival males, writing that “guarding individual females may represent the most efficient breeding strategy for males.”
Both Shultz et al. and Lukas and Clutton-Brock use models to simulate and prove their conjectures, but the way they present the data within the article alters the way a specific audience may interpret the data. Typically, casual readers approach scientific journals and articles visually, glancing at the diagrams and graphs before moving the textual evidence. If the diagrams are too complex or uninteresting, then a casual reader would simply stop and skip the rest of the article. On that note, Shultz et al. provides a diagram detailing their results, however the probability and proportions provided are not well explained in the description (to a casual reader at least). This complexity is opposite of Lukas and Clutton-Brock, whose figure 2 is a simply flow chart without any data. Their data is provided within the textual discussion, should the reader find the interest to dig deeper. In addition, Lukas and Clutton-Brock acknowledge certain counterarguments, such as those posed by Shultz et al, in their discussion, pointing out possible reasons their results differ, such as “some species that we classify as socially monogamous were classified by Shultz et al. as group living.” This adds to their credibility by demonstrating that they are knowledgeable with other hypotheses, to the point where they can point out differences in other experiments.
After reading both articles, I am still not convinced on either theory, however the two experiments have sparked my interest on this topic, in addition to bolstering my understanding of concepts that are related to social monogamy, such as mate protection and parental care, which were discussed in class. While the experiments were both well designed and orchestrated, I cannot choose a side knowing so little about the topic, but these articles are a start. It must be noted that even though I have not subscribed to any single theory, that does not mean that the articles were uninteresting. I was surprised to read that, despite both studies mentioning that the male usually makes the decision to remain with one female, the ancestral human case seems propose the opposite: that the female chooses to remain faithful to the male.