Social monogamy stems from a mating strategy in which males find it more favorable to stay and ensure the survival of a few offspring from one mate instead of simply increasing the number of offspring from different mates. This way, males guarantee their offsprings’ viability and survival, which also guarantees the perpetuation of their genes. Mammals exhibit K-selection, prioritizing the survival of their offspring over the number. Although they have fewer offspring, they are also more likely to survive and reproduce.
Christopher Opie et al. states that, according to ancestral-state reconstructions and model rate parameters, infanticide risk is the only trait that appears before the movement from polygynandry to monogamy in primates. The other two traits mentioned, mate guarding and paternal care, are the results of monogamy.
D. Lukas and T.H. Clutton-Brock state that monogamy evolved as a result of intolerant breeding females, and low female density. Parsimonious phylogenetic reconstructions show that nearly all of the species studied by Lukas and Brock came from ancestors that had solitary females and roaming males. The females preferred a diet that was high in nutrition but not readily available, which explains the low female density.
Lukas and Clutton-Brock admit that male infanticide is less common in monogamous species, but phylogenetic analyses and BayesTraits’ models show that the traits evolved independently. It both surprised and interested me that both papers used infanticide as a point in their papers, though I believe Lukas and Clutton-Brock make a more convincing argument because they consider and refute the male infanticide argument made by Opie. Male infanticide is not very common in most monogamous species: according to Lukas and Clutton-Brock, only 27% exhibit it.
The needs of the offspring affect the types of relationships within a species, and the types of relationships impact the care the offspring receive. In class, we discussed how monogamy seems counterintuitive from an evolutionary perspective because it reduces diversity, but depending on the offspring and competition in the environment, monogamy in primates may be more practical just as when the needs of the offspring are low, so is the need for monogamy.