Jennifer Tucker, an associate professor of history and science in society at Wesleyan University, is the author of “Nature Exposed: Photography as Eyewitness in Victorian Science.”

THE now infamous beliefs about pregnancy that are held by Representative Todd Akin — the Republican nominee in a hotly contested Senate race in Missouri, who remarked earlier this week that the female body will try to “shut that whole thing down” in the case of “legitimate rape” — are obviously at odds with modern science. They are, however, in step with medieval science, even if Mr. Akin doesn’t seem quite aware of the similarities.

In the Middle Ages, as the historian Thomas Laqueur has written, there were two different views of reproduction. According to the Hippocratic model, both parents made seeds from materials throughout their bodies, a process called pangenesis. Both male and female seeds were needed to make a new person.

A second theory of reproduction was offered by Aristotle. For Aristotle, everything in nature is composed of both form and matter. Form is what makes a particular thing that something: it is the kiwi-ness of a kiwi. But that form is expressed in matter appropriate to the form: you can’t make a person out of kiwi matter....