Do we need a study for this? I think we have known this fact for years and we have that X chromosome that accounts for this. Some other medical factors that relate here too is the fact that women also get pregnant and pay higher premiums for health insurance too, perhaps it may have something to do with the various levels of responsibility the female gender has to carry so we bond, that’s nothing new, and those who have other issues can be seen on the Jerry Springer show (grin). BD
Men are more likely to reproduce and therefore to benefit from numerous short-term partners. For women, however, quality seems to be more important than quantity. Also for women, finding partners of high genetic quality is a stronger motivator than sheer number, and it is commonly believed that women are more willing to have casual sex when there is a chance of forming a long-term relationship. As Professor Campbell explained: "In evolutionary terms women bear the brunt of parental care and it has been generally thought that it was to their advantage to choose their mate carefully and remain faithful to make sure that their mate had no reason to believe he was raising another man's child.