It need not be the case that sperm from multiple partners is simultaneously present in the female — just that there operates some sort of differential sorting mechanism that privileges some matings over others. In any case, it is generally becoming accepted that models of sexuality that imply females to be coy and passive in the face of aggressive male sexual ardor are seriously at variance with the facts — whether in humans or other animals Gowaty, ; Hrdy, ; Judson, ; Zuk, It has been suggested that vaginal contractions during orgasm can increase the chances of pregnancy as they transport sperm up the reproductive tract from the vagina to the oviducts, which decreases the distance it has to travel. As intercourse continues, these feelings grow stronger and stronger until the man has an orgasm and ejaculates, at which time semen then shoots out from the end of his penis into the woman's vagina. However, it must be admitted that these pioneering studies did not measure fluid movement per se — only the potential for such movement driven by uterine pressure changes. Recently, these multifarious and separate neural pathways of genital sensitivity have been mapped onto the sensory cortex Komisaruk et al.
There are those who argue that female orgasms help to cement pair bonds, in a species requiring bi-parental care Eschler,; Morris, ; Rancour-Laferriere,
C, Allen K, Brody S. These reactions may cause the man to ejaculate more quickly or to produce more semen; when a woman reaches orgasm during intercourse, it often makes her man have an orgasm at that point as well. They kept diaries of their periods and all reported regularity with them. In addition, each woman was supplied with a sterile 10 mL syringe body, which was to be used for both introduction and collection of the sperm stimulant, surgical glove, and spoon. All were white, European, or American and had been educated to at least undergraduate degree level.