Decoding Love - Andrew Trees [16]
WHY WE GAVE UP PARTNER SWAPPING FOR STABILITY
The question is, why? What force caused this behavior in human beings? The answer is quite simple: children. Our babies are born in an almost absurdly helpless condition and remain that way for a long time. Based on studies of modern hunter-gatherer societies (which roughly approximate our original evolutionary environment), children aren’t able to produce as much food as they eat until they are about fifteen years old. So, pair-bonding was likely a biological necessity. If women were left to raise the children completely on their own with no help from the father, many fewer children would have survived until adulthood—a far more ruthless calculus than what we find in the romantic story line and one that continues to have more relevance today than we care to admit. Have you ever wondered why evil stepparents are so often at the center of children’s fairy tales? It turns out that there is a good reason for this widespread cultural anxiety—a stepchild is sixty-five times more likely to be fatally abused than a child living with his or her biological parents.
But pair-bonding didn’t just happen overnight. Humans had to evolve in a manner that reinforced the pair-bond, which they did in a number ways. Let’s start with sex. The first question is, why even have sex? From a genetic standpoint, it is inefficient, since only 50 percent of your genes are passed to your child. There are plenty of other methods of reproduction—some of them positively mind-boggling—that have evolved in the natural world: multisexual for the swingers out there, female only for the feminists, bisexual for the indecisive, asexual for the squeamish, parthenogenesis (virgin birth) for the Christian, and even a few species in which the sex of an individual animal can change back and forth for the transgendered. We could easily pass along our genes far more effectively if we had gone down the path of asexual reproduction, for example. The problem is that this would have left us vulnerable to parasites, which evolve much faster than we do. How much faster? It took millions of years and roughly 250,000 generations for us to split from chimpanzees and become homo sapiens. For E. coli bacteria to experience a similar number of generations would take only nine years. So, sex was the method humans and other animals evolved to fight back against parasites. Simply put, sex allows for far more genetic variation and helps keep us from succumbing to our various bacterial and viral invaders—another classic Red Queen situation in which our evolving immune systems are working hard, simply not to fall behind the parasites attacking us.
When it comes to sex, men and women can congratulate themselves on being the great endurance athletes of the primate world. No, we can’t match chimpanzees or bonobos or many other species in the frequency of our sexual encounters, but we blow away virtually every other primate when it comes to the duration of our coitus. Pygmy chimps clock in at a lightning-fast fifteen seconds, which seems unbelievably short until you consider the common chimpanzee, which manages to get the job done in only seven seconds (although this does not mean that female chimps aren’t enjoying themselves. According to one study, female chimps can have an orgasm after only twenty or so thrusts). This is roughly on par with baboons, who take about fifteen pelvic thrusts. Gorillas come in at a leisurely one minute. Meanwhile, the average American couple has barely begun, averaging a full four minutes. We are bested only by the orangutan, which averages about fifteen minutes for copulation, but we’ll leave them to one side since they are obviously busy getting it on with one another.
As always when you find this sort of discrepancy in behavior, evolutionary thinking demands an explanation, particularly when there is an obvious downside to increasing the length of copulation. First, during the act, you are vulnerable to attack, and second, the longer you have sex, the more precious energy