10 Things You Didn't Know About Sexual Biology (Male Edition)

The Female Edition of this article was well-received and it got me excited to start working on this, the Male Edition. Turning my focus to the obscure factoids related to male sexual biology was certainly fun, but something bugged me throughout the process. In comparison with the attention that women get when it comes to scientific studies, men are neglected. The very fact that there is no universal or scientifically accepted way to measure the size of a penis should tell you all you need to know about that. Furthermore, studies on penises are usually done on patients for sexual dysfunction, rarely on subjects who are perfectly healthy. With that said, I think I have 10 really interesting facts that you might like hearing about. Here we go!

1. Humans have the largest penises out of all primates. In fact, the animal that you'd expect to have the largest, a gorilla, averages a 1.5 inch penis. You don't want to be hung like a gorilla. So, how did humans come to possess such large sex organs? It could be a result of our upright progression. Our postures allow a multitude of sexual positions which cannot be performed without a large enough willy.

2. Penis sizes vary across ethnicities, races and regions, but condom sizes are standard. This increases the overall HIV risk of cultures with smaller or larger than average penises. A survey done a couple years ago concluded that over 50% of Indian men have penises about an inch shorter than the international standard used to size condoms. A bad fit for a condom means that it is more likely to break during intercourse or that men will completely forgo using them out of frustration. This factoid shines a little light on societies with high rates of HIV, bringing another element of concern to the cause of safe sex. Before you can get people to wear condoms, you have to make sure they fit.

3. Humans might get "boners," but we don't have penis bones. Other mammals do, though. Chimpanzees, dogs, cats, bears, and whales all have penis bones. They're there to facilitate quick mating, allowing the male to penetrate without an erection. Just insert tab A into slot B a few times and it's done. We should be happy that we don't have them because we like to have fun. However, the absence of a bone will not prevent the penis from actually breaking. That can certainly happen and it is most frequently reported in the instance of an overzealous woman on top suddenly putting her weight awkwardly down on a semi hard-on. If this happens, get thee to a hospital.

4. Blue balls is caused by blood trapped in the pelvic region, unable to drain out. When a man becomes aroused, the veins in his pelvic region expand with the release of nitric oxide through the blood stream. Conversely, the veins leading out of this region contract, trapping the blood inside. When an orgasm occurs, everything gets relaxed to its normal state, but when the body doesn't get what it is expecting, things can get painful. The blood becomes starved of oxygen, which is like early necrosis. Thankfully, the body doesn't stay fooled for long and relaxes itself before things get out of hand.

5. Testicle size in relation to body size is directly correlated with average promiscuity of the females of a species. The more promiscuous, the bigger the balls. Think of it this way: if you know there's competition, you're going to bring more soldiers to the battle. Larger testicles produce and store more sperm, allowing males to compete in an arms race of microscopic proportions. Chimpanzees are all about free love, and because of this have quite large testicles. Gorillas, meanwhile, are generally monogamous, experiencing very little sexual competition, thus they have very small testicles (That's strike two for gorillas). Humans fall between these two species, as you might expect.

6. From the start, less than 15% of a man's sperm is even healthy enough to reach an egg. Like an Ironman race, out of 150 million sperm released in the average ejaculation, only a small portion are even fit enough to cross the finish line. The rest are deformed, unable to swim, double-headed, sickly or even dead on arrival. This is just fine because only a perfectly healthy sperm is able to penetrate an egg. Actually, a man is quite lucky if even 15% of his sperm is healthy enough (Dr. Harry Fisch, Columbia University Medical Center), but there are ways to improve that...

7. Sperm from men who watch hardcore (man + woman) porn swim faster than sperm from men who watch lesbian porn. Sexual competition does more than recruit more swimmers, it strengthens them, too. (Leigh Simmons, 2005) Witnessing the act of copulation gets the competitive juices flowing, preparing sperm for a fight. The result is more, healthier and stronger sperm released with each ejaculation. Lesbian porn does not produce the same virtual environment because there are only women in view and the brain interprets that as "more for me!" Further evidence of this can be found in comparison with other primates, where Chimpanzee sperm swim significantly faster than (you guessed it) gorilla sperm.

8. Semen is designed to subdue a woman's immune system so that it doesn't attack the sperm. As sperm make their way from the testes, out through the urethra, they are combined with several fluids from different glands. These fluids do many things like neutralizing acidity or even energizing the sperm. The most interesting elements of semen are prostaglandins, which act like a Jedi security force, waving their hands and convincing the female's immune defenses not to destroy the hapless sperm. These are not the droids you are looking for.

9. Women can be allergic to semen. When informed of this, a friend of mine insisted that he personally test his wife for allergies as he rushed out the door. It's true, though. There can be proteins in a man's semen that set off allergic reactions, causing itching and burning. Fortunately, there is a way to reduce any allergies to semen that one might have. Through frequent and repeated exposure, a person can become desensitized and lead a normal life. Remember that the allergies can relapse, so it is important to keep treating them. (Of course, if the allergic reaction is more serious than just itching and irritation, a doctor should be consulted.)

10. Pythagoras believed that semen was a "clot of brain containing hot vapour." No wonder we can be pretty stupid when we get turned on.

Thanks for reading. I hope you enjoyed the experience as much as I did while writing it. As a reward for your attention, I have a few bonus facts for you:

- 2.5% of Italian military recruits have micropenises.

- In "stretched penis" measurement studies, Koreans get the short end of the stick.

- 85% of women are satisfied with their partner's size, but only 55% of men are satisfied with their own penis.

- The clitoris is the only single-purpose organ in the entire body, out of both men and women. Its only purpose is to give a woman pleasure.

- Women are more likely to experience discomfort during sex with a circumcised male than with an uncut partner.

- There is conflicting research against the effect of circumcision on HIV contraction rates. This is mostly because research is non-standard, comparing men of different education levels and living standards.

- Male honey bees mate only once in their lives. Their penises break off inside the young queen with the force of their ejaculation and they fall to the ground where they starve to death in a matter of hours. This all takes place in mid-air, by the way. The next male comes along, pulls out the last penis and blows his top soon after.

Stay tuned for the Couples Edition.

(A big thanks to Sharon Moalem for his book "How Sex Works")