This is Shlain's third outing, and his formula is now apparent. He trumpets some ambitious theory about why we do what we do, basing it on the simplified dichotomy of creative female "right-brain" thinking and logical male "left-brain" thinking. For support, he employs a frothy mix of mythology, history, cultural studies, medical observations (he's a surgeon by day), and a loosely interpreted version of natural selection.
His last book, 1998's The Alphabet Versus the Goddess, posited that the written word empowered linear male thinking at the expense of the image-based feminine kind. The book found an appreciative audience in certain circles, creatively minded drumming circles not the least of them.
In Sex, Time and Power, Slain argues that menstruation — a rarity among species — gave humans a huge evolutionary advantage. The period provided a natural clock to teach us about time. Women used this newfound dimension to make a connection across the nine lunar months from sex to the painful, potentially deadly process of childbirth. Realizing what caused that misery, they became a lot more selective about who they'd get it on with, preferring studs who came courting with dead animal carcasses. Why? Meat had iron. Women craved iron, due to an iron deficiency spurred from the blood loss of menstruation. The smart male hunters used this tool of time to study the migration patterns of the animals — all the better to guess when and where to lie in wait.
Biologists toil for years to pinpoint the evolutionary purpose of some tiny trait, say, the spots on a certain butterfly. In contrast, Shlain explains how the entire human race evolved, namely by piling speculation on top of speculation. But he fails to establish clear links for a lot of what he presents. How do we know, for instance, the horny hunters didn't develop a sense of time first, using the seasons to predict the return of the meaty dinners?
Sex, Time and Power has its charms: Shlain has a talent, rare among science writers, for building suspense. He also drops in much intriguing historical and scientific tidbits. But as for the book's overall actual scientific validity, well, just be wary of any book on natural selection that does not once reference The Origin of Species.