Polygamy is the most common relationship seen in animals, as it allows for the male to increase the probability of passing on their genes. While females have a shorter window for fertilization and fewer gametes, males have a virtually unlimited number. Females are always sure that the offspring is theirs, but males cannot be certain unless they practice monogamy. Based on what we have discussed in class, monogamy may be rare, but to some mammals (mostly primates), it may be more reasonable for the two parents to stay together. Since mammals practice k selection and raise their young, it makes sense that the pair stays together to ensure the development of their offspring. This would allow the offspring to have a greater chance of survival, another method of increasing the longevity of the parental genes. In the two articles, there are different posed reasons for this social monogamy in primates.
Lukas and Clutton-Brock, in The Evolution of Social Monogamy in Mammals, point to the transitions to social monogamy. In this article, through analysis of over 2000 species and their living arrangements, they come to a conclusion that female intolerance led to the evolution of social monogamy. As stated in the article, “Solitary living appears to have been the ancestral condition for the ancestors of mammalian orders…”(526) Paired with the graph (Fig. 1) that mentions that low population density is more common with social monogamy (527), the authors come to a conclusion that solitary females mate with males that do not have the energy to guard the whole territory, leading to more prevalence of monogamy and paternal care. Lukas and Clutton-Brock go on to further explain, narrowing it down to where “feeding competition between females was intense, breeding females were intolerant of each other, and population density was low.” (529)
Opie et al. come to a different conclusion in the article Male Infanticide leads to social monogamy in primates. As stated in the title, the scientists here found that, of the three leading hypotheses at the time, the most likely was that social monogamy came about due to male infanticide. With male infanticide preceding social monogamy and a higher likelihood of monogamy in “the presence of high infanticide, the authors of this article point to this as the major pressure. While this article only focuses on analyzing three things, they find that of the analyzed correlated evolutions, only high male infanticide “consistently preceded the appearance of social monogamy across primates.” (13392)
The Lukas and Clutton-Brock article and the Opie et al. article come to opposing conclusions, but the former does it through more extensive analysis and more direct conclusions. Lukas and Clutton-Brock only focus on the relative presence of male infanticide and what happened to it after monogamy comes about. The authors take the correlation and turn it into causation. The other article takes it to another level, analyzing 2500 species and their living patterns, suggesting a plethora of ideas and debunking infanticide as a cause at the same time. While one article lies on the pillars of correlation and assumption, the other uses comparative analysis to find similarities between thousands of species. They pinpointed “six transitions to social monogamy,” (526) using them to find the pressures to this selection and disproving other hypotheses for social monogamy.
Going by the article The Evolution of Social Monogomy in Mammals, my idea of monogamy was originally way off of the truth. I thought that monogamy was just assurance that the offspring belongs to the father, and that is grows up to pass on the genes again. This aligns more with the male infanticide article, where the father keeps the offspring alive despite other males. This article saying that social monogamy stems from the intolerant females is on the opposite spectrum, since I thought it was the choice of the men and prioritizing their genetic longevity. To be fair, it is not only the females and intolerance, but also the population density, not allowing for males to easily go from female to female. Still, I was surprised that women have most of the power in this sense. This led to social monogamy, which supposedly led to some forms of paternal care in males. I realized that monogamous females had a consistent power in their reproduction, just like they do with most sexual dimorphism. This is a common theme in wild, and here, males are the ones that give a little.