It’s time for a talk. The talk. Yep, S-E-X. Sure, your parents probably busted out the anatomy books when you were a kid. That goes there, those do that, etc. (Yuck!) And you may have taken some sex ed classes in school, or had frank discussions with your doctor. But here’s a dirty secret: When it comes to human sexual anatomy—the wellspring of civilization—there’s a shocking amount people don’t know. Not just civilians. Scientists!

Part of it’s practical: Sex is really hard to study. Even today, with sensors and MRIs showing us what goes on when we’re getting it on, sterile labs aren’t exactly the coziest places in the world to examine our bodies. But much of the problem is also cultural: Until the Kinsey Institute, broaching the subject of sex at all was almost universally taboo. In other words, we humans don’t know our bodies as well as we think. (Remember Sophia’s very educational vagina lesson on Orange is the New Black?)

So we decided to own up to our ignorance—and take it one step further: We’re a dude delving into the depths of the vagina and a lady sizing up the science of the penis. There's more to anatomy than gyno charts and tutorials—we discovered a bunch of myth-busting, pleasure-validating developments in the field. And we want to talk about them.

Jason Kehe: So yes, we’re proceeding from the assumption that we don’t know much about human sexual anatomy—but let’s perhaps qualify that by considering this: Is it actually the case that we basically grasp the penis, but the real mystery is the (uh, largely ungraspable) vagina?

Katie Palmer: Sure, there are still people arguing—scientists arguing, in the medical literature—over the most basic parts of the female anatomy. There’s one father-daughter research team out of Italy that recently published that the female vaginal orgasm is a myth, because the G-spot doesn’t exist. Which has problems on so many levels.

JK: The chief being, of course, that the female vaginal orgasm is not a myth. Even if the G-spot isn’t technically a “spot”—in the way that, say, the clitoris sort of is—plenty of research has shown that stimulation of that (clitourethrovaginal) complex results in a deeply felt, full-body orgasm. Science suggests it’s harder to achieve than, say, a clitoral orgasm, which is enjoyed more locally and externally.

KP: It’s so nice having you tell me what I enjoy.

JK: Well, I’m constrained by thousands of years of patriarchal tradition. Anyway, male orgasms aren’t as controversial because they’re as simple as—well, is there white stuff or not? There’s rarely a question of whether climax was actually reached.

KP: Gross. Obviously I won’t let you get away with that—there’s a lot more to male orgasm. First of all, “the white stuff”—that’s ejaculation, but ejaculation and orgasm are two totally different things. The orgasm goes on in your brain; it’s associated with an enormous surge in dopamine, and then oxytocin, and of course a number of other complicated neurotransmitter pathways that scientists don’t completely understand yet. Ejaculation, on the other hand, is controlled at the level of the spinal cord. It’s like a reflex. Even if your brain can’t communicate with your penis—like in men with spinal cord injuries—you can still ejaculate. Once you’re aroused enough, your body reaches the point of no return and has no choice but to shoot out semen.

JK: OK, so ejaculation and orgasm in men are distinct (though I’m going to assume they go hand in hand [or wherever] most of the time). It’s actually not so different in women. In addition to vaginal orgasms being real, female ejaculation is real (and distinct) as well, according to most mainstream sex researchers. I spoke with Beverly Whipple, who helped popularize the G-spot back in the early ’80s. (Funny story: A colleague originally suggested she call it the “Whipple-Tickle”; Beverly, bless her, said no way. She preferred “Gräfenberg spot,” or G-spot, after its original discoverer.) In Whipple’s words, female ejaculation resembles “watered-down” or “fat-free milk,” and only about a teaspoon is released at a time (“released” being preferable to the other popular verbs in the literature, like “expelled” or, forgive me, “expressed”). Whipple adds that, despite mankind’s historical suspicion of womankind’s orgasmic expulsions, Western civilization has actually been documenting female ejaculation at least since Aristotle—though back then, you’d probably describe it as the nectar of the gods.

By the way, female ejaculation is not—repeat, not—the same thing as the phenomenon known as “squirting” or “gushing,” whereby the woman...well, I think the words speak for themselves.

KP: Wait, so that has a different composition than a woman's normal lubrication?

JK: Sure does! Though again, this is a controversial subject. Some researchers dismiss any female emission as “vaginal hyper-lubrification”—so, just a lot more of exactly what you mention. But that’s probably pretty inaccurate. On one end of the what-fluids-come-out-of-the-nethers spectrum, you have your basic urine; on the other, you have the aforementioned nectar of the gods.1 “Squirting,” however, seems to fall somewhere in between—though, according to the latest research, it’s likely much closer to the urine side. There’s not a ton of work being done in this area, but thanks to the French (natch), we’re now a bit more certain that squirting is almost entirely urine. In a recent study, French doctors showed that a squirting woman’s bladder fills up during sex and then gushes out (of the urethra) during orgasm. Of course, they only studied seven women, and all of them reported “massive emissions” to begin with, so it’s possible that they’re all just incontinent during sex.

Also, I should add: There’s this idea, I’m guessing due to porn, that “squirting” is the ultimate expression of a woman’s pleasure, but there’s really no evidence to back that up. For now, most sex researchers agree that squirting and ejaculation are distinct events. Squirting is mostly pee, with trace amounts of prostatic secretions (yes, women have a prostate, also known as Skene’s glands); ejaculation is, biochemically, much more complex. For instance, it’s been shown to contain sweet-tasting sugar molecules!

KP: Semen has fructose too! Along with a bunch of other things, from five different glands, all mixed together. There’s zinc, and citric acid, and, obviously, sperm. I was surprised to learn that the majority of the volume comes from the seminal vesicles, not the vas deferens. Funnest fact: Semen is also basic, to cancel out the acidity of the vagina and keep the woman’s inhospitable hellhole from killing all the sperm it’s trying to make babies with.

JK: Does eating pineapples really make it taste better?

KP: Whaaa…?

JK: Never mind.

KP: OK, we’ll lay aside that particular myth and examine another one. Like, for example, what would you say is the average penis length?

JK: My somewhat educated guess is 6.5 inches.

KP: Flaccid, erect, or stretched?

JK: Assuming “stretched” is some perverse reference to medieval torture chambers, I’ll say erect.

KP: So, unsurprisingly, you overestimated. In case you haven’t checked on the international averages lately: Average erect length is about 5 inches, and flaccid length is around 3.5 inches. And unfortunately, stretched length is a thing that scientists measure—that’s about 4.8 inches on average. (One study had abnormally high “stretched” numbers because the methodology included 3 tugs before measuring.) US averages might be slightly higher than international averages—a recent study put erect length at 5.6 inches. ’Murica! Whether or not they’re actually below average, men are obviously closely attuned to their differences—to the point where some men are seeking out penile prosthetics.

JK: I blame Mark Wahlberg. Anyway. What’s interesting is, women have concerns about their anatomy as well: Vaginas, just like penises, come in many shapes and sizes (see: the Labia Library—probably NSFW), and women can surgically redecorate. Speaking of fixing what’s broken, we must touch on erectile dysfunction.

KP: OK, but before we do, can we clarify how erection happens, period?

JK: Isn’t it just blood pumping it up?

KP: Way more complicated. My favorite study title so far is “Erectile hydraulics: Maximizing inflow while minimizing outflow.” But there’s a lot of interesting biology before the blood can flow in, and then stay in. The most important part of the penis for an erection is the corpus cavernosa—two spongy cylinders, surrounded by muscles.

JK: Hey, women have those, too! Leading back from the clitoris. Same evolutionary idea.

KP: Sure, so when men get aroused, a cascade of neural signals goes from the brain to special nerves in the penis, which release a neurotransmitter—nitric oxide, or NO. That chemical starts a molecular messaging pathway that causes the muscles in and around those cylinders to relax, letting blood rush in. Pressure from muscles and the hard penis itself presses on a network of veins, keeping the erection going by preventing blood from flowing out.

JK: Understood. What could possibly go wrong?

KP: So, so many things. Erectile dysfunction can be because of problems in the brain, or in your overall body (like how well your body oxygenates its blood, which is why obesity can be a major risk factor for ED), or in the penis itself (like if the free nerve endings in the head aren’t sensitive enough to transmit signals to the brain and initiate arousal). Any of those can make erections difficult to initiate or sustain. But ED obviously also has a lot to do with a man’s perception of his performance relative to what he’s heard from his friends, or what his partner has experienced.

JK: I’m so glad you mentioned culture (again). It might not be the case after all that vaginas are more mysterious than penises—but it occurs to me that they might be more divisive. Do people have strong opinions on penises? Sure, they’re weird-looking, and they carry a lot of baggage—including, most symbolically, centuries of male aggression/domination. But people, at least people I know, don’t really get worked up about them. Vaginas, by contrast, seem to inspire a whole range of opinions, from passionate devotion to eternal dread.

KP: A greater degree of comfort with the penis does sort of make sense in the context of biology. Men are showers (most, anyway)—the putative indicator of sexual prowess is on display all of the time. Some evolutionary biologists think that before clothes, penis size developed as much as a lure to the opposite sex as a functional entity (to be fair, does anyone trust evolutionary biologists anymore?). So much depends on how people perceive that organ. Women, obviously, don’t have their fertility on display 24/7. So there would be more mystery and misunderstanding associated with the vagina.

JK: Which makes one wonder: Is it more difficult for women to orgasm actually, or culturally? Again, science seems to suggest it really is harder, but lifetimes of “mystery and misunderstanding” could be partially to blame. Anyway, I fear we’re straying too far from the science—and that, ultimately, is what we need more of. The future of man—and woman—depends on it.

More from the WIRED Sex Issue:

1Correction appended, 2/13/18, 5:05 PM EDT: KP: Not out of vaginas, Jason. Pee comes out of urethras.