Thomas A. Foster is an associate professor and chairman of the history department at DePaul University. He is the editor of "Documenting Intimate Matters: Primary Sources for a History of Sexuality in America."

Rep. Todd Akin, the GOP's candidate for U.S. Senate in Missouri, caused a huge stir the other day with his comments about how women who are true rape victims rarely get pregnant.

"If it's a legitimate rape," he said, "the female body has ways to try to shut that whole thing down."

In a piece that was typical of the widespread outrage the remarks stirred, the Atlantic magazine called them the "contemporary equivalent of the early American belief that only witches float."

The writer was onto something important. Akin's ideas truly do date back to the colonial era.

In those days, prior to modern medical understanding of conception, women were considered to be "more amorous" than men, and it was believed that both partners needed to have orgasms in order for conception to occur....