Posted on Fri 13 December 2013

Everything I never knew about sex I learned from this book

A note to start: this blog post is about sex. Or, to be more specific, the physiology of sex. If that's not interesting to you, or if you're offended by reading about genitals and the like, feel free to skip this one.

So, why am I writing a blog post about sex? Simply because I just finished reading an excellent book that explored the history of scientific study into human sexuality and there were some points in it that were so fascinatingly mind-blowing that I had to share them.

So this is just a wrap-up of my favourite parts of the book and some thoughts on what I learned from it.

Bonk: The Curious Coupling of Science and Sex by Mary Roach

You can find this New York Times bestseller on Amazon. Mary Roach has also written books about other interesting taboo topics like digestion and cadavers, so if you like her style, you should check those out as well.

I read mine on my Kindle, so I've looked through my highlights and grabbed the ones that I found most important/interesting to share with you. Prepare to be amazed (but also note: my understanding of sex is—or at least, was—very limited, so some of this might not be at all shocking or new for you).

Okay, we all know that our bodies are smart, and they're geared towards procreation. But they're even smarter than I had realised.

... uterine contactions—minor peristaltic versions of which are happening all the time, not just during orgasms—have been shown to reverse direction over the course of a woman's menstrual cycle. Around ovulation, when a woman is most fertile, they pull material in toward the uterus; during menstruation they expel it.

It doesn't stop there, though:

Not only do sex hormones orchestrate the direction of your uterine contractions, they dilate only the fallopian tube that contains the ovum, so that more semen ends up on that side.


Moving over to the male reproductive organs, here's a tidbit I found fascinating:

... few had realized how much of the penis lies hidden below the surface of the skin. The "root" is nearly two thirds again the length of the "pendulous part."

That's quite a bit of penis to have hiding inside you without knowing it's there.

And again, there are some super smarts going on from the male's side of procreation:

... the last portion of a man's ejaculate contains a natural spermicide—not intended to kill his own soldiers, obviously, but to annihilate the seed of any who come after him.

There's also a ridge on the head of the penis (more prominent in some) the effectively scrapes semen out of the vagina as it exits.

Around this point of the book came a fascinating section about the morally questionable methods and torturous devices used to stop people masturbating in the past. It focussed very heavily on men and nasty "treatments" to keep their hands away from their penises, so I'm going to skip this section since I'm not trying to make you squirm. I do recommend it though, it's interesting, if horrifying at times. I'll also skip the highlights I made about where in the world (and why) penis re-attachment surgery is most popular. Keep an eye out for that one.

So let's move on to a surprising passage about sperm:

Sex physiologist Roy Levin explained to me that sperm which sit around the factory a week or more start to develop abnormalities: missing heads, extra heads, shriveled heads, tapered and bent heads. All of which render them less effective at head-banging their way into an egg. Levin speculates that that's why men masturbate so much: It's an evolutionary strategy. "If I keep tossing myself off, I get fresh sperm being made."

But wait, regular masturbation isn't quite as good as it sounds:

Though if conception is the goal, you don't want the sperm to be too fresh. Daily masturbation would deplete the number of sperm per ejaculate... To produce an ejaculate with optimum potential for fertilization, Levin recommends a holding time of five days.

Time for some womanly facts now. This one in particular blew me away (I'll leave you to read about what the dildo-camera is in the book, unless you've already seen it in the first episode of Masters of Sex):

The dildo-camera unmasked, among many other things, the source of vaginal lubrication: not glandular secretions but plasma (the clear broth in which blood cells float) seeping through capillary walls in the vagina.

Plasma. That clear stuff in your blood. The stuff you donate to the Red Cross instead of whole blood cells—that's what vaginal lubrication is. Mind blown.

In fact, my mind was actually blown when this came up again later in the book and I fully understood how it works:

When a woman is turned on by something or someone, her brain sends a signal to open up more of the capillaries in her womanly recesses. This ups the amount of blood in her vaginal walls, and some of the clear portion of it seeps through the capillaries and coats the vagina. Hello, lubrication.

If you donate plasma at the blood bank, as far as I know it works like this: a needle in your arm takes your whole blood cells out through a tube, then the plasma gets separated and kept, while the leftovers are yours to keep—i.e. whatever's not plasma gets put back into your arm.

And yet, look how clever the female body is at separating plasma from your blood! Amazing.

It's also nice to know it's not some kind of mucus. Somehow it seems a bit more scientific and less gross knowing its part of your blood, I think. Plus, apparently "No other lubricant can compare with it in efficiency for a certain smooth and slippery quality..." Well, there's no arguing with that.

Speaking of female lubrication, one of the most important things I read in this book was about how female arousal works. If you take one thing away from this blog post, take this one. Take it and tell all your friends. It's that important.

The fact is this: for women, the body (i.e. the genitals) and the mind are very separate when it comes to arousal. One can often be highly aroused without the other responding:

Lubrication from "reflex arousal" (physical stimulation of the genitals) can occur with absolutely no subjective emotional arousal. Levin also points out that fear causes the release of adrenaline, and adrenaline increases blood flow to the genitals. Which, in turn, enhances lubrication (or erection in men).

The reason fear comes up here is because an example of where this is important information to know (and the biggest reason why I want to share it) is in the case of rape, or other unwanted sexual contact. The point is, particularly for women, the genitals may respond to being stimulated even when the mind is not interested at all. A woman could be repulsed, scared for her life, or simple just not interested, and yet be responsive physically.

Regardless of the mechanisms that may or may not explain a rape victim's physical state, a rapist's defense based upon evidence of arousal has, to quote Levin, "no intrinsic validity and should be disregarded."

On that note, let's move on to another example of where the body is smarter than I'd realised. One of the researchers Mary talks to in this book is focused on automatic muscle reflexes that occur during sex. This was one of my favourites:

At the same time as the vaginocavernosus reflex is affecting the clitoris, Shafik found, it's also putting the squeeze on the man's dorsal vein, helping trap blood in the penis and keeping it firm.

Something I learned earlier in the book was about how erections work. In case you're unfamiliar, it's all about blood. The inside layer of the penis fills up with blood, and as it does it pushes against the outside layer, putting pressure on veins (including the dorsal vein) to stop the blood from leaking out. As the pressure subsides (e.g. after ejaculation), the blood drains through these veins.

So this quote is saying that during sex, the vaginal muscles naturally help keep the penis hard. Not only is that super clever, it's good for everyone.

Just for fun

A few last unrelated points that I found amusing:

One of the less prominently known similarities between pigs and men: They both fondle breasts. No other males on the planet regularly do this.

A business anthropologist is someone who, among other things, helps corporations avoid cross-cultural misunderstandings. For example, the one that led PepsiCo to run an ad in the Chinese Reader's Digest that said, "Pepsi brings your ancestors back from the grave!"—rather than the intended "Come alive with Pepsi!"

A comforting word about the crooked penis. Dr. Hsu says it is rare to see one that stands perfectly straight. Actually, what he said was: "Most men are communists! Leane to the left! Second most common: bow down, like Japanese gentleman! Number three, to the right. Four, up! Like elephant!"

Nasal congestion is an erection inside your nose.

I promise, that one actually makes sense when you read the book!

One last one, off-topic but fascinating:

Nominations for a Nobel Prize, I found out when I contacted the Nobel Foundation to try to verify Shafik's, remain secret for fifty years. You make the claim, and nobody can prove otherwise until after you're dead.

Well, you're all equipped for your next dinner party now. Plenty of facts to keep the conversation going. Enjoy!

Oh, and don't forget to pick up the book. You'll get to find out about all the stuff I didn't mention, like why pandas are bumbling lovers, and what the Penile Pricking Ring is. And of course, I know you're dying to know more about the dildo-camera, aren't you?

P.S. I make some stuff you might like: Exist, a personal analytics app to help you understand your life, and Larder, a bookmarking app for developers.

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