As its provocative title suggests, Why Is the Penis Shaped Like That? (Scientific American, 320 pages, $16) is a book unafraid of topics most of us don't typically have the balls to bring up.

It's perhaps an unfortunate choice in title gimmick, as research psychologist Jesse Bering's essays have more breadth and depth than it suggests. Besides profiling the penis, Bering also explores laughter, religion and cannibalism from an evolutionary angle. Cannibalism, he argues, is part of humanity's evolutionary repertoire, no more a perversion than vegetarianism or a strong sweet tooth. Many of the essays also delve into sexual preferences Western society has deemed perverse or the result of mental illness, including foot fetishes and the neurology of pedophiles.

Bering's findings have obvious ethical implications. He invites readers to form their own opinions, but his remain clear. His moral musings eventually question the very notion of free will, since all a body's kinks and quirks are the result of unalterable brain chemistry. Is it Joe's fault that he's turned on by giraffes? Or if he enjoys the taste of human flesh?

Bering thinks not. However, he says people are responsible for how they act upon these urges. You may not be able to blame pedophiles for a biological affinity for little boys, but that doesn't excuse their behavior. Presenting an unflinching look at our society's mores through empirical research is risky, but Bering handles it well.

In so many other ways, this book could go very wrong. Thankfully, Bering manages to dodge most bullets. He doesn't hide behind psychobabble, yet he grounds his conclusions in research. The jokes come fast and readers will find themselves thoroughly entertained by his cheekiness, but he doesn't leer over the juicy details. Instead, his candid approach succeeds in putting even the most bashful at ease, allowing them to get over their own discomfort long enough to learn something about penis shape. 

GO: Jesse Bering will speak at Powell's City of Books, 1005 W Burnside St., on Wednesday, July 18. 7:30 pm. Free.