The secret life of semen
New Scientist, 25 August 2006
MEN may contribute more than just sperm to the babymaking process - their semen may coax things along as well.
fluid is regarded as primarily a carrier agent for sperm. It is thought
to increase sperm motility and strength but not actually affect the
woman's body. Indeed, IVF clinics rinse the semen from sperm and
discard it. But now Rebecca Burch, at the State University of New York
at Oswego, has found some intriguing compounds in semen.
particular, hormones. Some found in semen, such as follicle-stimulating
hormone, luteinising hormone and estradiol, are known to induce
ovulation. FSH actually causes the egg to ripen and burst out of the
ovary. Others, such as human chorionic gonadotropin and human placental
lactogen have a role in maintaining pregnancy.
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
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
Sure enough, compared to humans, the semen of chimp
males had significantly lower levels of FSH and no luteinising hormone
whatsoever. Burch presented her results earlier this week at the
meeting of the International Society for Human Ethology in Detroit,
Michigan. IVF clinics should consider not rinsing away the semen, she
told New Scientist.
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