We've known for a long time that males from many species tend to be interested in sexual variety, particularly in having more than one partner. A missionary visited a Maori village in 19th century New Zealand and there was a feast in his honor. And they'd rather have three than two. As Margaret Mead once pointed out, monogamy is the most difficult of all marital arrangements. For some time, biologists have had a good idea why.
Men are sperm makers.
Sperm are cheap and easily replaced. Unlike eggs, they do not require that the guy doing the fertilizing become pregnant, give birth and then nurse his young. So the interesting thing about the Jackson affair isn't Jackson's behavior. Rather, it's why Karin Stanford, his paramour, went along. And here, biologists have finally begun to catch up with common sense.