Monogamy is something that very few species of mammals actually practice. Scientific teams seem to think that they have found a reason why, but dueling teams don’t have the same answer. The answers that they do have however are less than romantic.
One team looked at primates only, which includes monkeys and apes. They claim that monogamy started in this group so that the father could protect the offspring from being killed by another male.
The other team looked at over 2,000 different species of non-human animals. They found that the mammals developed monogamy because the females had spread out so much geographically that the males needed a way to fend off the competition. Dieter Lukas of the University of Cambridge states that it is not about love. He states, “It’s just really the best he can do”. Not so romantic now is it?
Both teams said that having two parents instead of one to raise the offspring was a side benefit, but not a main reason for monogamy. They say romance must have come after because it was also not one of the main functions of a monogamous relationship with these species.
The studies were published in the journals Proceedings of the National Academy of Sciences and Science. The mammal paper discounted humans as research subjects, while the primate study included them. Both teams are hesitant to apply their findings to humans because of its less-than-romantic notions.
Christopher Opie was a lead researcher on the primate study. He says that there are 25% of the primate species that are socially monogamous. There are some animals such as gibbons that are extremely monogamous, and then there are others like chimps that are at the other end of the spectrum.
Opie took data from 230 species of primates and how they behaved and then he mapped out evolutionary family trees for them. He used over 10,000 computer model runs and calculated mathematical probability and came up with a timeline for when certain traits appeared. In this timeline he found that before monogamy there was a very high rate of offspring being killed by outside males.
Tim Clutton-Brock was the author of the all mammals study and he stated that he did not see a spike in infanticide rates but found instead that solitary females came before monogamy. They had to spread out in order to get food that was of good quality which made it easier for multiple males to find them. Lukas stated that the males cannot defend more than one female, so they stuck around and monogamy was born.
Both teams, after doing their research, agreed that they would not put humans in a monogamous category because the traits that were expressed in true monogamy such as what was seen with the gibbons were not traits that most humans possessed.