There's a gene found in rats that influences their interest in mating for life. Whaddayaknow -- humans have it too, and wedded bliss is related to who has the gene. Men without the gene had happy marriages and were more likely to be married in the first place. Men with one copy of the gene are largely single or unhappy, but guys with two copies are most likely to show up in the tabloids. I'm looking at you, Mr. George Clooney.