Free Decoding Love by Andrew Trees Page A

egg. Most now consider this idea far-fetched, but it is safe to say that sperm and eggs are locked in an evolutionary arms race and will likely remain that way indefinitely.
     
    Males are not defenseless in this high-stakes genetic game. One strategy they have evolved is virtually relentless copulation to ensure paternity. Some mammals have even developed copulatory plugs—their ejaculate contains a substance that literally blocks the sperm of rival males. While human males don’t have anything quite so medieval sounding, they have their own “weapons.” One recent study has theorized that the ridged glans on a man’s penis is designed to scoop out a competitor’s semen, and the last part of a man’s ejaculate contains a natural spermicide, a kind of before-and-after protection system against female promiscuity. Researchers have also done a study comparing the ejaculates of men who spent 100 percent of their time with their wives with men who spent less than 5 percent of their time with their wives. The result? Men who have been absent ejaculate with almost twice as much sperm—712 million versus only 389 million. Also, human semen contains prostaglandin, a hormone that can cause uterine contractions and thus undermine the selectivity of the female orgasm. This suggests that men also have some very finely honed evolutionary devices to try to ensure the paternity of their offspring.
     
    Even on the level of genetic code, men and women are locked in conflict, as Matt Ridley has shown in his fascinating book Genome. At some point in the past, humans switched from the reptilian method of determining sex by the temperature of the egg to a genetic method, which allowed for specialized sex genes to develop. But this is a volatile situation because what is good for one gene can be bad for another gene. For example, the ability to seduce is a great gene for a Y chromosome, but the ability to resist seduction is good for the X chromosome. If one chromosome could strip a quality from another chromosome, that would be a huge advantage for one sex. The problem is that the genetic battle between X and Y is not really a fair fight, because the X chromosome can dominate the Y chromosome. Women have an XX chromosome, and men have an XY. For every one chance a Y chromosome has at undermining something in the X chromosome, the X chromosome has three shots to do the same thing. In this instance, the sexual arms race is a slaughter, and the Y chromosome has done the only sensible thing—run away and hide. To do that effectively, it has become small, very small. While the X chromosome has more than one thousand active genes, the Y chromosome has only twenty-five. Over time, it has basically shut down all but a few essential ones. This gives the X chromosome very few targets to go after and helps make sure that the genetic arms race doesn’t end in complete surrender. Little did you know that the struggle to find Mr. or Ms. Right was being fought even on the genetic level of individual chromosomes, and that a woman’s X and a man’s Y are busy trying to stick it to each other.
     

DATING AND DECEPTION
     
    Given this ceaseless battle on both the human and genetic level, relationships are rampant breeding grounds for deception. Part of the problem is that modern society provides far more opportunities to lie. In our ancestral environment, social groups were smaller, and those who lied would gain a reputation for dishonesty. But in today’s environment, especially in cities or other highly populated areas, there is a much smaller chance of being caught. Internet dating has only increased the problem. Not surprisingly, men and women in relationships lie to each other all the time. In a 1990 study of college students, researchers found that 85 percent of the participants had lied to a partner about a past relationship or an indiscretion. Another study revealed that dating couples lied to each other in about one-third of their