Scientists have now looked at MHC compatibility among romantic couples and they report that the more genes in this system that a couple share, the more sexually unfaithful the woman is and the more she is attracted to other men during in the middle of her menstrual cycleâ€â€Âwhen she is ovulating and likely to get pregnant.
I guess this explains why women find exotic men irresistible. Read more at; http://helenfisher.typepad.com/helenfisher/2007/02/lovefrom_from_a.html