Monogamy Schnogamy

Based on the textbook reading, the reason for monogamous relationships is multifactorial.  The environment influences a species’ engagement in monogamous relationships through the cost of offspring.  If the offspring requires more food and care than the mother can supply, there is a higher rate of monogamous relationships and paternal care, because the presence of the father increases the fitness of the offspring by helping to care for the offspring.  Also, the certainty of paternity plays a part in whether a species is monogamous.  Species that have external fertilization have a higher rate of engaging in monogamous relationships, than species with external fertilization because the certainty of paternity is higher with external fertilization.  The father would not want to waste their energy and reproductive potential caring for an offspring that might not be theirs.  There is also a genetic component involved with monogamous relationships, as seen in the prairie voles that engage in monogamous relationships, partly because of male prairie voles’ higher concentration of V1a receptors.

The Opie, Atkinson, Dunbar, and Schultz article makes the claim that social monogamy in primates is a result of male infanticide.  The scientists determined that social monogamy results from: the cost of raising offspring is too high so the mother must rely on the help of others, females have discrete ranges making it hard for males to mate with more than one female, and infanticide rates are high enough that males are needed to provide protection against infanticide males.  Infanticide occurs so the female can return to estrus cycle (the cycle when they are able to reproduce), because the female delays the estrus cycle when in order to avoid feeding two infants through lactating at the same time, because lactation is longer than gestation.  Based on their likelihood based phylogenetic comparison methods, Opie, Atkinson, Dunbar, and Schultz came to the conclusion that social monogamy is a result of infanticide because of all three of the possible hypotheses, it is the only one that precedes social monogamy in the models.

Lukas and Clutton- Brock assert that social monogamy is a result of the ancestral behavior of mammals being solitary individuals, and monogamy is derived from that.  Lukas and Clutton-Brock’s two hypotheses for social monogamy are paternal care is needed for carrying the offspring and/or to prevent infanticide, and also mate guarding, because males are unable to guard more than one female.  Lukas and Clutton-Brock used likelihood reconstruction approaches to determine that for 99% of mammals, the female ancestors were solitary and the male ancestors roamed.  This solitary condition led to female competition, female intolerance, and low female densities, which led to social monogamy because males were unable to defend multiple females.

The Lukas and Clutton-Brock article makes a more convincing argument, because they use ancestral evidence by tracing the evolution of mating behavior to social monogamy, and then draw their conclusions from there.  The other article had hindsight bias by only examining their three hypotheses, and left no room to discover other reasons for social monogamy.  Also, the Lukas and Clutton-Brock article disproves the other infanticide and male care hypotheses.

The Lukas and Cutton-Brock article has changed my view on social monogamy in primates, because of its bulk of evidence.  The most surprising thing reading this article was that primates commit infanticide to increase reproduction.  It is such a horrible act to us humans, but for the primates, the ends justify the means, because they have a higher chance of perpetuating their genes through infanticide.

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