Christopher Ryan and Cacilda Jethá continue to plug their book on the evolution of human sexuality. On infidelity:

With the caveat that every situation is different, one factor we think deserves more attention is the role of testosterone (T) in middle-aged men’s eroticism. In their twenties, men’s T levels begin a long decline, often experienced as diminished passion and appetite for life. Suppressed T levels are associated with depression, heart attacks, dementia, and overall mortality rates from 88 to 250 percent higher. One of the few things that can reliably and immediately revive a man’s sagging testosterone is exposure to a new woman. One researcher found that even a brief chat with an attractive woman raised men’s testosterone levels by fourteen percent within minutes. In Sex at Dawn, we suggest that many men may be confusing the hormonal changes triggered by an affair with actual “love,” thus leading them to make ill-advised decisions catastrophic to their families, their marriages, and eventually themselves.

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