I don't think men are hardwired to be monogamous.
Sorry for the double post, but there is some truth to this.
Men are more likely, biologically speaking, to want to sleep around as they (we) want to have the maximum possible spread of genetic material possible to maximise the chance of our genes being carried on. Women are more likely to want a monogamous relationship as it provides a more stable environment in which to raise any offspring.
On an unrelated note, I also find the position in menstrual cycle/different type of man theory to be pretty interesting.
I should have done an anthropology degree.