Ain't misbehaving

http://www.economist.com/science/displaystory.cfm?story_id=9401551

FROM an evolutionary perspective, monogamy looks good for females and bad for males. For mothers, it means devotion as dad is going to be around to help look after the kids. For fathers it is more of a prison sentence, because it restricts a male's ability to inseminate lots of females at relatively low cost. In most circumstances, unless the young are likely to die without paternal support, a male has little incentive to stay with an individual female when he has so many other females to breed with.

That, at least, was the conventional wisdom until fairly recently. But modern genetic techniques have shown that in many species females in apparently monogamous relationships often produce families that have more than one father. To explain this, biologists have theorised that these females are mating with males who are genetically superior to their regular mates, thus getting the benefit of parental assistance from a cuckold and good genes from a Lothario.