Credit: Slug Signorino

Why is it that exposure of the female areola and/or nipples is considered pornographic while exposure of the male areola and/or nipples is not? I read your answer to the question "Why do men have nipples?" and it seems that, physiologically, nipples are nipples. So why the different reactions? —Sheryl, Michigan

Listen, Sheryl. You know how in some cultures men can show their uncovered mugs in public but women have to wear a bag over their heads? Same idea. Now if what you're really wondering about is the rationale behind the double standard on nipples, fine, let's walk through it.

1. Female humans are the only primates with permanently enlarged breasts, which has led to much harebrained speculation about why. I'm not about to add to it. I merely cite my favorite theory, from zoologist Desmond Morris's 1967 The Naked Ape (I elaborate somewhat): (a) male apes mount their paramours from behind; (b) female apes are only in heat at certain times; (c) as a signal that the female ape is sexually receptive, her buttocks become enlarged and red; (d) humans generally do it face to face, and women may be game at any time; (e) any billboard of human female availability thus would logically be installed permanently in front; (f) inasmuch as the female breast becomes enlarged anyway during lactation, it's the obvious candidate. In other words, men like the female breast because, at a primordial level, it reminds them of a monkey's butt.

2. It's not just women's partners who like boobs. Most women find their breasts a source of sexual pleasure—more than eight in 10 report playing with their breasts and nipples increases their arousal. That said, while the nipple is the most sensitive part of the breast, sex play tends to involve the breast as a whole, not the nipple in particular—excessive concentration on the latter is likely to get your partner annoyed.

3. The male nipple is also a source of sexual pleasure—more than half of men report playing with their nipples increases their arousal. So the argument that the female nipple alone must be covered because it's an erogenous zone and the male nipple isn't won't wash.

4. Exposure of much (as distinct from all) of the human female breast is decidedly not taboo. On the contrary, it's the basis of entire industries.

5. For much of the world, seeing a nipple or two is nothing to freak out over, but in significant parts of the U.S. the unspoken assumption seems to be that, except in narrow circumstances, the exposed female nipple is the equivalent of public fornication. Absurd, you say? Keep reading.

6. Sex being the freighted topic it is, many Americans apparently need a bright line between saucy but permissible display of the female breast vs. indecent exposure. Judging from state law, there's a surprising diversity of opinion on what that bright line is. Some states prohibit exposing any part of the breast, while others ban everything below the top of the nipple or the top of the areola—nowadays a none-too-realistic standard adhered to by such backward localities as Massachusetts. West Virginia, interestingly, comes closest to nailing what in my opinion is the de facto standard, as evidenced on the red carpet at entertainment industry awards ceremonies: it permits display of "any portion of the cleavage of the human female breast exhibited by a dress, blouse, skirt, leotard, bathing suit, or other wearing apparel provided the areola is not exposed, in whole or in part."

7. For the definitive word on this subject we must turn to the U.S. Supreme Court. In City of Erie v. Pap's A.M. (2000), the justices took up the question of whether Erie, Pennsylvania, was legally empowered to prohibit totally nude erotic dancing by women, the difference between illegal total nudity and acceptable partial nudity being that, to comply with the law, "dancers had to wear, at a minimum, 'pasties' and a 'G-string.'"

Pap's argued that Erie was unconstitutionally infringing on its right to freedom of expression. Piffle, said the court: "Even if Erie's public nudity ban has some minimal effect on the erotic message by muting that portion of the expression that occurs when the last stitch is dropped, the dancers…are free to perform wearing pasties and G-strings. Any effect on the overall expression is de minimis."

But never mind the strangely arousing juxtaposition of strip-club jargon and Latin. Look at Erie's SCOTUS-approved ordinance: "A person who knowingly or intentionally, in a public place…engages in sexual intercourse, . . . appears in a state of nudity, or . . . fondles the genitals of himself, herself or another person commits Public Indecency." Nudity is elsewhere defined as including an uncovered female nipple but not a male one.

Ponder the significance of that. A man walks around bare-chested and the worst that happens is he won't get served in restaurants. But a woman who goes topless is legally in the same boat as if she'd had sex in public. That may seem crazy, but in the U.S. it's a permissible law. —Cecil Adams