Can men ever know how caressing the clitoris or vaginal lips makes women feel? Can women ever know how fondling the head of the penis or the scrotum makes men feel? The short answer is no. If you don’t have a clitoris, you can’t know how it feels.

But that’s not the whole story. Male and female genitalia both develop from the same embryonic cells and they’re wired into the the same way. The genders don’t differentiate until late in fetal development. While one can’t know precisely how erotic stimulation makes the other feel, an understanding of genital embryology can help lovers appreciate each others’ bodies and pleasure more intimately.

The embryonic cells that become the head of the penis (glans) in men become the clitoris in women. As a result, touching the clitoris feels like touching the glans—except for one thing. The clitoris and the glans each contain some 7,000 sensory nerve endings, a greater of touch-sensitive nerves than any other part of the body. But the clitoris packs them into a volume only about one-tenth the size of the glans, so touch for touch, this concentration of nerves makes the clitoris more sensitive than the glans.

This super-sensitivity is the reason why, unless the woman requests otherwise, the clitoris should be caressed very gently. In , the men sometimes rub the way you rub sticks to ignite a fire. That’s too rough. Many women feel discomfort—even pain—when men are not very gentle. Even when fondled gently, direct pressure may be hard to take. There is nothing wrong with women who feel this way. If a woman is super-sensitive, a lover should not fondle directly.

The embryonic cells that become the penile shaft in men become in women the inner vaginal lips (labia minora), the clitoral shaft (the little cylinder that connects the clitoris to the body), and the -spot, the erotically sensitive area an inch or two inside the vagina on the front wall, the top if the woman is on her back. Touching these areas feels to women like stroking the penile shaft feels to men.

Like the penile shaft, the inner lips, clitoral shaft, and G-spot contain many nerves sensitive to erotic touch. They also contain erectile tissue. As women become sexually aroused, minor erection of the inner lips helps open the vulva, making the vagina more accessible for intercourse.

The outer lips develop from the same embryonic tissue that forms the scrotum. Touching the outer lips feels to women more or less like fondling the scrotum feels to men.

Most people consider the vagina a key female organ, for some, the only one. But the embryonic tissue that becomes the vagina has no connection to the sexual tissues discussed above. It develops from the Mullerian ducts, tissue that degenerates in the male.

Biologically, the vagina is less about sex than reproduction, the gateway to the world, the birth canal. Compared with the clitoris and vaginal lips, it contains few nerve endings. Although intercourse may feel marvelous and cement and closeness, biologically, the vagina is not that central to the erotic experience.

The vagina is a sex organ to the extent that the G-spot is accessible through it. The vagina is also a sex organ for men because it receives the penis during intercourse. But using that definition, the mouth is a sex organ because it, too, can receive the penis.

Unfortunately, the sex media show men pumping fingers, penises, sex toys, and other things furiously in and out of the vagina. Most women would feel more sexually satisfied if men gently caressed the clitoris, vaginal lips, and G-spot—which feels rather like erotic touching of the head and shaft of the penis and the scrotum.