On the origin of orgasms in women
Not evolution -- 'for fun,' expert says
Dinitia Smith, New York Times
Tuesday, May 17, 2005
Evolutionary scientists have never had difficulty explaining the male orgasm, closely tied as it is to reproduction.
But the Darwinian logic behind the female orgasm has remained elusive. Women can have sexual intercourse and even become pregnant -- doing their part for the perpetuation of the species -- without experiencing orgasm. So what is its evolutionary purpose?
Over the last four decades, scientists have come up with a variety of theories, arguing, for example, that orgasm encourages women to have sex and, therefore, reproduce, or that it leads women to favor stronger and healthier men, maximizing their offspring's chances of survival.
But in a new book, Dr. Elisabeth Lloyd, a philosopher of science and professor of biology at Indiana University, takes on 20 leading theories and finds them wanting.
The female orgasm, she argues in the book, "The Case of the Female Orgasm: Bias in the Science of Evolution," has no evolutionary function at all.
Rather, Lloyd says, the most convincing theory is one put forward in 1979 by Dr. Donald Symons, an anthropologist. That theory holds that female orgasms are simply artifacts -- a byproduct of the parallel development of male and female embryos in the first eight or nine weeks of life.
In that early period, the nerve and tissue pathways are laid down for various reflexes, including the orgasm, Lloyd says. As development progresses, male hormones saturate the embryo, and sexuality is defined.
In boys, the penis develops, along with the potential to have orgasms and ejaculate, while "females get the nerve pathways for orgasm by initially having the same body plan."
Nipples in men are similarly vestigial, she points out. While nipples in woman serve a purpose, male nipples appear to be simply left over from the initial stage of embryonic development.
The female orgasm, she says, "is for fun."
Lloyd says scientists have insisted on finding an evolutionary function for female orgasms, either because they are invested in believing that women's sexuality must exactly parallel that of men, or because they are convinced that all traits have to be "adaptations" -- that is, serve an evolutionary function.
Central to her thesis is the question of how often women experience orgasms during sex. She analyzed 32 studies, conducted over 74 years, of that frequency.
When intercourse was "unassisted" -- that is, not accompanied by stimulation of the clitoris -- just one-quarter of the women studied experienced orgasms often or very often, she found. Five to 10 percent never had orgasms. Yet many of the women became pregnant.
Lloyd's figures are lower than those offered by Dr. Alfred Kinsey in his 1953 book, "Sexual Behavior in the Human Female." Kinsey's studies found that 39 to 47 percent of women reported that they always, or almost always, had orgasm during intercourse.
But Kinsey, Lloyd says, included orgasms assisted by clitoral stimulation.
Lloyd says she has no doubt that the clitoris is an evolutionary adaptation, developed to create excitement leading to sexual intercourse and then reproduction.
But "without a link to fertility or reproduction," Lloyd says, "orgasm cannot be an adaptation."
