Semen may have more functions in reproduction than merely being a carrier of sperms. A researcher from America reports that the semen from fertile men contains a multitude of hormones. Some of them like, FSH (Follicle Stimulating Hormone) initiates ovulation. Some other hormones are reported to have a role in the maintenance of pregnancy.
The researcher, Rebecca Burch, thinks human males have evolved the concoction as a counter-strategy to concealed ovulation in women. Although there are subtle chemical cues that a woman is ovulating, there are no overt signs. So at any given copulation, a male wanting to reproduce could be wasting his time. Semen that could help induce ovulation while his sperm are in her reproductive tract would be a great advantage, she says, as would compounds that could bolster a new conception and help the fertilised egg implant.
If this was an evolved strategy, Burch reasoned, species where ovulation is not concealed would not need it. To test her theory, she asked colleagues at Yerkes National Primate Research Center in Atlanta, Georgia, to test the semen of six chimpanzees. Unlike humans, chimp females advertise their fertility with bright red swollen behinds.
Roger Gosden, at the Center for Reproductive Medicine and Infertility in New York, says he doubts that enough of these compounds could get into the female bloodstream to make a difference, but says he and others remain "mystified" by semen's composition.