When you said "nipples," I thought perhaps Einstein had said something about gestation that I missed, perhaps about why men have nipples and mammary glands that we obviously do not need. As Stewie Griffin once experienced, if we tried to nurse, the babies would get hair in their milk (assuming we had active mammary glands, which we don't).

It's actually a fascinating topic. To simplify it, as I understand it, we all start in the womb as female. Males don't even start developing uniquely male characteristics until three months in the womb, when the nipples and mammary glands are in place.

Then this is the part I'm kind of not quite clear on. The gestation process only removes or alters that which must be removed to form males. Since our primary sexual characteristics are not in any way impeded by the presence of nipples or mammary glands, they remain.

The mammary glands in males typically remain dormant. But they do activate and enlarge in males with gynecomastia. Bodybuilders who abuse anabolic steroids often experience this, though they typically call it "bitch tits."

It's learning things like this that caused me to reject creationism when I was young and embrace evolution. We're actually very inefficiently designed.

Hold your hand up, with the fingers straight. Now bend one finger at the base. Just one. I used to think this worked because the brain told that single finger to bend. That's not the way it works. What actually happened is that your brain sent an impulse to all your fingers (except the thumb), telling them to bend. A later "overlay" in our evolution then told your remaining three fingers to remain straight. So, to bend one finger, your brain tells all your fingers to bend, then a millisecond later tells three fingers you don't want to bend to remain straight.

Can you imagine the number of impulses that my fingers experienced just to do the intricacies in typing this post?

Though I'm a Christian, looking at this thoughtfully made me think that this (and other mechanisms) argued against what we now call "intelligent design." We were not designed intelligently. We're a mass of baseline impulses that can only modify baseline actions with a series of overlays. It doesn't sound like we were designed intelligently; it sounds we evolved.

I'll address the actual topic when I come back from the gym. Just enjoying the learning I experienced that this topic header brought to mind. Sorry to wander.

@"why men have nipples and mammary glands that we obviously do not need"

I think the reason men have nipples is actually quite simple: We have them SO THAT we can pass on the genetic encoding for constructing nipples to our daughters, who DO need them. This in itself IS an important use - i.e. carrying genes for our offspring. (And there is simply no evolutionary need or selection pressure to construct some system for hiding or suppressing our nipples simply because we don't use them.)

It's a little like the genetic equivalent of a man holding a woman's handbag - "I'm just holding onto this for someone else." Except in this case it's the genes he's holding onto, and that someone else is his female offspring.

In every man and every woman is the genetic encoding required to construct either a female or a male ... a woman still holds the genetic material to construct penises not only to construct her own clitoris but also because her sons will need those genes to construct penises.