Two weeks ago, I saw a review on our Weddings page of a book called “Sex at Dawn: The Prehistoric Origins of Modern Sexuality” (HarperCollins). Without much thought, I blurted out in a tweet that it sounded pretty stupid to me. But that started a surprising e-mail conversation with one of the authors, Christopher Ryan. It’s interesting not only for what Mr. Ryan says, but as an example of the way patient authors can profitably engage even caustic critics[.]

—Ron Charles