As the school year ends, May and June are typically quietertimes for Indiana University faculty, Not so for ElisabethA. Lloyd, the Arnold and Maxine Tanis Chair in IU Bloomington'sDepartment of the History and Philosophy of Science. In May,Harvard University Press published her new book, whose titlemay explain why Lloyd was suddenly busy. It's called The Case of the Female Orgasm: Bias in the Science of Evolution .

Lloyd's analysis of past evolutionary studies of human sexualityfound an audience of millions. Articles and segments about thebook ran in hundreds of newspapers, magazines, radio and televisionstations around the world. For several weeks Lloyd shuttled backand forth between her office, WFIU-FM's sound studio, and NewYork to answer questions and discuss her work.

Because one of Lloyd's more provocative conclusions is thatthere is no compelling evidence to suggest the human female orgasmhas any evolutionarily adaptive significance, most inquirerssimply wanted to know, "What's it for, then?"

Lloyd, also a professor of biology at IUB who has researchedsexuality and its scientific study for 20 years, told NewYork Times culture writer Dinitia Smith simply, the femaleorgasm "is for fun."

"At least two main biases have negatively affected theevolutionary explanation of the female orgasm," Lloyd writesin her book's introduction. "One of them is the bias ofassuming that the female orgasm evolved to its present form inhuman beings because it contributed to the reproductive successof its possessor in some way."

The other bias, Lloyd believes, is that the vast majority ofresearchers have assumed female sexuality and male sexualityare equivalent.

The (approximately) 1:1 ratio of male orgasm and sexual intercoursestrongly suggests an evolutionarily adaptive origin in men, butthe loose relationship between orgasm and intercourse for women-- Lloyd cites statistics that suggest as few as 20 percent ofwomen reliably experience orgasms during sexual intercourse-- makes the female orgasm a less potent and reliable force inimpelling women to reproduce.

It is more likely, Lloyd says, that the female orgasm is primarilya vestigial characteristic in women, like nipples on men. Itexists because human beings of either sex grow from the sameembryo, and therefore share many physiological characteristics.Despite their divergent appearance, male and female sexual organssimilarly have much in common, for example, the clustering ofnerve endings in the male penis and female clitoris. But thatdoes not mean, Lloyd argues, that sensations induced by the organsserve the same purposes.

The Case of the Female Orgasm was partially fundedwith a grant from the National Science Foundation. Lloyd countsamong her book's benefactors Anne Fausto-Sterling, Richard Dawkins,and Bruno Latour, as well as IU Bloomington's own Ellen Ketterson,Noretta Koertge, and former Kinsey Institute Director John Bancroft.