Promiscuity: An Evolutionary History of Sperm Competition Chapter 2

I recently recommended Dr. Tatiana's Sex Advice to All Creation to someone and was reminded that I had Promiscuity waiting for me on the shelf upstairs. Over the next few posts I'll jot down a few notes and afterwards boil those down for your perusal along with a few of my personal observations. It should be noted that these posts will likely be extraordinarily graphic and thus not recommended for the faint of heart. That said, they should at least be interesting but don't expect it to hang together like a proper narrative since I'm just going over my notes, not retyping the whole text.

Chapter 2

Birds, it turns out, are total sluts. Studies indicate that 70% of bird species engage in sex outside their brooding partnership. A notable example is the purple martin; when given access to a multi-apartment birdhouse in the spring, the entire house will be first taken over by one male who will protect it fiercely until he attracts a mate. Once he has his mate in place and she's attending her nest he'll invite other males to join the household and when they do so he'll also have his way with their mates as well. Genetic studies show that the dominant male in fact fathers half the offspring in the entire complex. The amount of sluttiness (and the success of it) seems to be directly related to just how different the males look from the females. Apparently females need a particularly studly-looking guy to make it worth the effort.

On the flip side, monogamous females are relatively rare and when they do occur it's usually under somewhat unusual circumstances. Among some insect species which reside in dormancy underground before sexual maturity, males will actually dig up dormant females and copulate with them before they are fully developed. Some butterflies even go so far as to have a long, hard penis which can penetrate the female's pupal casing. Even more bizarrely, female angler fish support their tiny male counterparts for life. The male lodges himself inside the female and sucks her blood to stay alive ready at any moment to perform his function.

The Corydoras Catfish takes no chances with the father of her children. When mating the female places her mouth directly over the male's genitalia, sucks his sperm out and reissues it through her own genitalia seconds later to fertilize her eggs. Male seahorses and pipefish are similarly cautious since responsibility for the eggs lies with them. The female lays her eggs in the male's brood pouch and only after the eggs are secure does the male fertilize them by himself with a box of tissue and some hand lotion.

While the female is out seeking the attentions of others the male is working on a plan of his own to keep her faithful. The most common of these is 'mate guarding.' In many species the male will simply follow the female wherever she goes when he senses she is fertile. For insects, the last male to copulate with a female has an advantage over those who have come before so they tend to guard their females after the act. One extreme is the male dungfly who will hang on his mate's back for 20 minutes while she lays her eggs to ward off any latecomers. Alternatively, some species of shrimp have reproductive processes which favor the first male to copulate with a female. Males range far in wide in search of virgins and in some cases will go so far as to pick up an immature female and carry her around for several days until she's ready to be fertilized. Depending on the male to female ratio a male may cart around a woman for 9 whole days before he has his way with her and leaves her forever.

If a male can't guard his mate he may resort to just doing it with her over and over again. Giant water bugs have been known to copulate 100 times in 36 hours during periods of egg laying. Birds may do the act from 1 to 500 times over a single clutch of eggs.

Promiscuity: An Evolutionary History of Sperm Competition Chapter 1

I recently recommended Dr. Tatiana's Sex Advice to All Creation to someone and was reminded that I had Promiscuity waiting for me on the shelf upstairs. Over the next few posts I'll jot down a few notes and afterwards boil those down for your perusal along with a few of my personal observations. It should be noted that these posts will likely be extraordinarily graphic and thus not recommended for the faint of heart. That said, they should at least be interesting but don't expect it to hang together like a proper narrative since I'm just going over my notes not retyping the whole text.

Chapter 1

The Greeks, due to a surfeit of dead male soldiers to dissect had a really good idea of how the male member worked. The female form, however was a different story since dissection of a woman was strictly forbidden. Having observed various ob-gyns over 10 years of marriage it seems clear to me that not a lot has changed in the past 2000 years. The text admits, for example, that science currently doesn't know what physical function the clitoris performs. My wife, however, says SHE has a pretty good idea.

Erasmus Darwin introduced the concept that males in a species have secondary sexual characteristics such as large plumage displays or dangling wattles to attract females of the species in his 1792 text Zoonomia. In the 1960s, Bob Trivers postulated that the showiness of these displays is inversely proportional to the male's involvement with the young. To offer proof by anecdote, the peacock has a tremendous sexual display but his responsibilities end immediately after he inseminates the hen. Inversely, the male magpie invests heavily in his mate bringing her food throughout the entire brooding process and he is virtually indistinguishable from his hen.

In 1937 Geoff Parker introduced the idea that this competitiveness may even happen at the level of individual sperm. Parker examined dungflies, a species in which the female is approached by several males and noted that as a female approaches a patty several males wrestle for the opportunity to mate with her. It's in the female's best interest, Parker argues, to be inseminated by as many males as possible. Similarly, the male is best served who can not only inseminate a female but protect her from insemination by others. At the same time males who can fight through the attempts of other males to keep females to themselves have an advantage. What results is an arms race between males who attempt to protect their mates from intruders but also to overcome the defenses of others. Meanwhile the female benefits as long as multiple males assail her honor. And to help her make the distinction the female has evolved all manner of chemical and physical processes to put the competing sperm through the wringer to select only the best.

Machine Gun versus Bazooka

Sometimes, it’s not just the size of the gun that matters but the ammunition. The fairy wren, for example, delivers bit time when it has sex. Each time this little tiny bird ejaculates he fires a monstrous 8 billion (yes, with a b) sperm. That’s 45 times more than the average human who puts out a piddling 180 million in each delivery.

So didn’t Bateman’s principle state that being a guy was the cheap end of the garter belt? What could possibly be cheap about 8 billion sperm and why would a bird less than 2 inches long need THAT many sperm? The answer, as you might guess, goes back to competition. Female fairy wrens are incredible sluts. Despite the fact that males assist in child rearing, genetic testing has indicated that chances are good that most of the chicks in a nest don’t actually belong to the male helping out. Because of the female’s behavior, males find themselves in the midst of an incredible arms race. Each sperm is a lottery ticket and the more lottery tickets the better.

Not all males who produce a lot of sperm do so because their women are sleeping around. Sometimes, high sperm counts are the result of just how hard is to get a sperm from the male to the egg. Many trees, for example, are pollinated by the action of the wind. They rely on the capricious actions of the weather to make sure that boy meets girl. These plants produce pollen by the bucketful because they’re literally at the mercy of chance. Others trees have the advantage of relying on active pollinators which carry pollen directly from one tree to the next. These species get away relatively cheap but make up for it to an extent since they must produce some gift in the form of nectar to attract the insects and birds that do the work of playing sexual middlemen.

In many higher species, the reason for higher sperm counts is even more bizarre. In humans, sperm counts are astronomical because the female’s anatomy is actually hostile to sperm. The human vagina is exceptionally acidic and it alone kills off 90% of the sperm deposited therein. 90% of the remainder are culled out by the mucus of the cervix and the rest are subject to the immune response of the female. White blood cells respond within minutes and start killing sperm by the millions. In traversing less than 12 inches within the female, 180 million sperm have been reduced to a few hundred. This overtly hostile environment helps to assure that only the healthiest sperm have a chance to fertilize the egg. An arduous 10-month gestation is, after all, a terrible thing to waste on some guy’s second-rate sperm.

Bibliography

Judson, Olivia, Dr. Tatiana’s Sex advice to all creation,
Metropolitan Books, Henry Holt and Company, New York, 2002.

If you must go out, go out with a bang

I often wonder how different the world would be if human males were more like male honeybees. Most male bees never actually get to have sex at all. They wander around looking for queens to inseminate for their entire lives. In this way, they are a lot like some human males. There are also the lucky bees though. These lottery winners of life actually find a woman, get to have sex, ejaculate, tear off their own penises, leave it stuck in the female’s vagina and then explode with an audible POP.

The obvious question in the reader’s mind will no doubt be a resounding and audible “Ewwwww, WHY?” Well, when your species doesn’t afford a lot of opportunity for you to have sex, this makes perfect sense. Most males never find a mate so when they do get that lucky, any act, no matter how self-destructive, can help their genes have a better chance of fathering the next generation of bees. Having a disembodied penis broken off in your vagina does have a definite negative effect on a female’s ability to accommodate the next lucky guy.

Only problem with this is that the female objects to this attempt at enforced monogamy. She only mates for a short time during her youth and after that she just uses sperm from that one fling to create an entire hive of bees. She’s got a lot invested in that one fling so if she only gets to mate with one male and that male happens to be genetically incompatible with her then she’s in deep trouble. She could spend the rest of her life turning out complete duds.

The other ‘only’ problem of course is the thousands of other male bees that want to have sex with the queen. Until they can figure out how to defeat the dismembered penis of suitor #1, they’re out of luck. Well, luckily for all involved, they’ve evolved an answer to the conundrum.. The male honeybee’s penis has an apparatus on it that happens to be just the right size and shape for prying a little tiny penis out of a female’s vagina. So suitor #2 simply approaches the queen, does a little light cleaning and then proceeds with copulation. It’s just the sort of odd foreplay that we’ve no doubt come to expect from the animal kingdom.

Luckily for humans, most other animals have less explosive devices for promoting their sperm over those of the ‘other’ guy. Many rodents produce a rubbery plug which they inject into the female to seal up the entrance after they copulate. To counteract this process, some species have evolved a prehensile penis to remove the plug (which they then eat to get a tasty pre-sex snack) and clear the way for his own sperm. Any attempt to apply these images and techniques to your own sex life is most strongly not recommended.

Bibliography

Judson, Olivia, Dr. Tatiana’s Sex advice to all creation,
Metropolitan Books, Henry Holt and Company, New York, 2002.

You and Your Penis

You can tell a lot about a person by his penis. The complexity of the penis seems to be related to the competition for females. Bushbabies and many other small primates have obscenely complex and fanciful penises with knobs, spikes, bristles and other accoutrements designed to stimulate the female to accept his sperm more readily. Competition for females among these groups is quite intense and any competitive advantage is worth the effort. Compare this to the male gorilla. He presides more or less unchallenged over a harem of females and as a consequence this 500 pound behemoth has a penis only 2 inches long. So much for the big-shoes/big-wang theory.

As usual though, the insect world has the world of mammals beaten by a mile. Damselflies have inflatable penises with horns and bristles that it uses to clean the female’s vaginal opening before copulation. Now that’s “washing that man right out of your… well, not hair…” Others have genitals so complex that females will forcibly eject the sperm of other suitors when a new male comes to mate, but only if he’s got “the right stuff.”

Sadly, most birds lack penises entirely. They must be content to just rub themselves together and deliver sperm that way. Nonetheless, males have devised ways to get rid of his rival’s sperm. Some will perform oral sex on the female to remove her other lovers sperm and some species have even evolved a ‘fake’ penis that it uses to scrape out the vagina before copulation. I guess all this explains the male obsession with tools.

Bibliography

Judson, Olivia, Dr. Tatiana’s Sex advice to all creation,

Metropolitan Books, Henry Holt and Company, New York, 2002.