Monogamy viewed—and defended—through a fish-eye lens:
In biology monogamy is defined as forming a pair bond with only one mate for the length of a breeding season. Throughout the animal kingdom monogamy is rare and there is a differentiation to be made between "social monogamy" and "genetic monogamy." Many species of birds have been observed to be socially monogamous. They build a nest together, incubate their eggs together and feed their chicks together. Therefore when scientists started using genetics to determine whether all of the chick were the offspring of the two parents they were surprised to find that in most species of socially monogamous birds over 10-25% of the chicks do not belong to the father! Why would this be? One explanation is that females don't want to put all of their eggs in one basket. Females are choosy and look for the best mate based on characteristics such as bright coloration or a complex vocalization....
What are the factors that lead to a monogamous mating system? The intensity of parental care needed to raise the young is one important factor. This point is made clear by a comparison of different marine reef-fish species.
Read the whole thing.