07/06/2010 03:36 pm ET | Updated May 25, 2011

Why Men Cheat: Science Says 'New' Women Boost Testosterone

Andrew Sullivan links to a blog post on male sexuality by Christopher Ryan, co-author, along with Cacilda Jetha, of the new book "Sex at Dawn: The Prehistoric Origins of Modern Sexuality." Ryan looks at the eternal question: Why do men, in particular middle-aged men, have affairs?

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