Sperm and superiority

The latest study offers an interesting twist on what women should look for in a man--good sperm. Okay, okay, I know the next question: how does one go about finding good sperm? Well, it turns out that all a woman needs to find is an intelligent man. A recent study discovered a clear link between intelligence (as measured by something called Spearman's g) and sperm quality. Since we are all shaped by sexual selection, this is not a shocking finding, but it does offer an interesting window into just how deeply that sexual selection has shaped our species. On first blush, most of us would probably assume that there were many good reasons for the development of intelligence that had nothing to do with attracting a mate. But this study suggests the possibility that we have put the cart before the horse. Perhaps sexual selection is actually the driving force behind the expansion in human intelligence, and the many other uses we find for our brains are actually just fortunate byproducts of that sexual selection. Who knew that dating might hold the key to human evolution?

Mars and Venus, Sperm and Eggs

Mars versus Venus

For a long time, “Men are from Mars, and Women are from Venus” became a kind of cultural shorthand to explain everything that went on between men and women. But I think there is a much better way to think about our sexual differences—men make sperm, and women make eggs. From this one simple difference, you can get a vast array of different behaviors (and not just in humans—you find the same distinction at work throughout the animal kingdom).

You see, sperm are cheap (sorry, guys, it’s really not a precious gift). Not just cheap to make but cheap over time because the man doesn’t have to worry about all those pesky details like carrying around an unborn baby inside of him for nine months, let alone breast feeding it once it is born.

But eggs are precious. A woman produces only one a month. If she gets pregnant, she is on the hook for another nine months and really another couple of decades. On top of all of that, there is a sharp limit on the number of children she can have during her lifetime.

So, what sort of behaviors should this lead to? First, women should be a lot pickier than men are about their sexual partners. And studies show that they are. Second, women should be much more interested in commitment, and studies show that is true is well. In fact, there are a slew of behaviors that stem from this distinction. But all of them add up to one conclusion: women are in the driver’s seat when it comes to dating.

Or at least they should be. There is a crucial wrinkle that changes this dynamic somewhat—monogamy. Legally sanctioned and enforced, buttressed by religion and society. Under those conditions, men start to become fairly choosy as well because it becomes a life-time partnership, not a one-night stand.

Ironically, women have a lot more control over the dating scene in a polygamous society than in a monogamous one. But I will leave that for another post.

PS If you are into the Mars/Venus distinction, the book you should read is Deborah Tannen’s You Just Don’t Understand, which laid the groundwork for the whole idea (not that she receives the credit she deserves). Her book is still probably the best single work on how men and women communicate in a fundamentally different fashion.