When it comes to lasting relationships, it seems that falling in love with your opposite is just what the doctor ordered.
A new research published in the journal, Psychological Science, by geneticist Christine Garver-Apgar at the University of New Mexico has found that in heterosexual couples, having a more similar a particular set of genes, that are linked to the development of the immune system, was not such a good thing for a woman’s sexual response to her partner, and that it was more likely that she would end up in the arms of another man.
As for why this may happen, well it seems that for women, hooking up with an opposite with a different immune system is a way to ensure that any kids born of the union will have a better and broader immune system, reports the Daily Mail.
A New Scientist article commenting on the findings, said that this attraction at the genetic level could one day mean that there will be DNA tests for women to check whether or not she is likely to stray.
However, Garver-Apgar insists that the likeliness to be unfaithful only increases if the immune system genes are alike, and is not limited to physical attributes.
The new study gives boffins another clue as to how people chose their mates.
Earlier studies had shown that both men and women prefer partners whose features are suggestive of good health and good levels of the hormones oestrogen and progesterone.
However, when it comes to women, their choice of partners sways from that of a "manly" man during the time of ovulation, to that for a more feminised, "nurturing" appearance at other times of the month.