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.
2 comments:
Wow! "This overtly hostile environment helps to assure that only the healthiest sperm have a chance to fertilize the egg."
My first reaction was -- No way. It just can't be ... after all, just look around you!
My second reaction was -- If this is true, then imagine how the world would be if just any old sperm got through! The horror!
Well, ya know... I'm not sure that healthy sperm make good people necessarily. All sperm have to do is swim their way through acid and muck without arms but one long tail. That's hard to extrapolate to human vehavior. :)
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