Monogamy: Infanticide or Isolation?

Based on what we talked about in class, we currently believe that parental care leads to the development of social monogamy in mammals. If offspring have significant needs that require more than one parent, a male may “increase his reproductive fitness’ by caring for offspring and being socially monogamous rather than searching for more mates. We determined that social structure would lead to the idea of group living, eliminating that option. Territoriality was also determined to have led to greater a risk increase and therefore less chance to care for your young or reproduce.

Opie, Atkinson, Dunbar, and Shultz believe that infanticide leads to the need for a “resident male can provide protection against infanticidal males”, which in turn led to the introduction of socially monogamous pairings. They claim that paternal care was a result of monogamy rather than the cause. They found strong evidence the “male infanticide precedes the switch to social monogamy”. Opie et al. also discovered that socially monogamous species “have lower risk of infanticide” and “once social monogamy evolves there is a high probability of a subsequent reduction in male infanticide”. In Lukas and Clutton-Brock’s article, they claim that “social monogamy is derived from an ancestral state in which females are solitary and male ranges overlap those of several females”. It was discovered that the “likelihood that the common ancestor was solitary is .99 for all approaches.” They also believe that due to changing diets, female populations became less dense, which in turn led to males having less control over a large range of females.

I believe that Lukas and Clutton-Brock made a better argument, as they used a wider range of species, as opposed to only primates. This made the argument seem more applicable to all socially monogamous species as opposed to only a small portion of the total. Also, the argument contained more data analysis and scientific proof, such as multiple BayesTraits’ tests and regression models (more math always seems more thoroughly tested). Lastly, they also had better counterarguments against each opposing argument, especially against the idea of male infanticide leading to monogamy, where they stated that few socially monogamous species have longer lactational periods than gestational.

I did not realize that most primates were socially monogamous because I had always just thought of them as living in groups. These articles enlightened me into the idea of the extent of parental care that primates attribute to their young, as well as the astonishing existence of male infanticide in primates (gorillas). I also did not realize that a majority of socially monogamous species come from ancestors that had female solitary living. The most surprising thing I read throughout the articles was probably that the idea of a changing diet could have led to the change from polygyny to social monogamy, which was just strange.

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