I have discovered evolution. I spent many years when enmired in Evangelical Christianity as a creationist who believed that life began in the Garden of Eden. I now know (if I know anything) that life evolved. I have studied this one extensively, and the evidence for evolution is everywhere, if you look for it. For example, I am now burning my way through The Moral Animal by Robert Wright (the author of The Evolution of God, one of the most transformational books I have ever read). Robert Wright is an evolutionary psychologist. That is, he believes that the phenomenon of human consciousness can be explained in evolutionary terms. I am finding this thesis very convincing.
I had a personal experience which demostrates the role of evolution recently. I take my dogs, Diogee and Napoleon, for a walk almost every day, weather permitting. Typically, we go for a 2 mile walk in the middle of the day, as close to solar noon as possible so that I can be exposed to natural UV light, which is really good for my health. More on this later.
I observe my dog Diogee (actually my wife’s dog, but I digress). Diogee has a behavior which Napoleon does not have: He scratches the ground after he does his business. He does so almost invariably, and he did not have to be taught to do this. He knew how to scratch the day I met him (and he was a very small puppy at that point). At the age of 10 (70 doggie years in other words), he still does this. So where did this behavior come from?
Viewed in terms of evolutionary psychology, it makes perfect sense. This behavior is the expression of a gene which Diogee has and Napoleon does not. At some point in the evolution of the dog (which is actually a wolf), there was some adaptation which caused the animal to bury his / her droppings. Possibly there were prey animals which used the droppings to identify the location of predators. If so, then burying the droppings would be a desirable trait. (In evolutionary terms, “desirable” means that the animal will be more successful at reproducing, and thus expressing this particular gene.)
Eventually, scratching after doing your business no longer had any significant benefit. Certainly, after humans took over the job of deciding how the canine species evolved (an event which happened in the mists of pre-history), the presence of dog droppings did not help prey animals to avoid being eaten. The archeological record is replete with evidence of how devastatingly effective a human hunting party was, when accompanied by a pack of domesticated wolves. All the humans had to do was use the dogs to drive the prey animals into a difficult area, like a swamp or a stand of canes. Once the prey animals were trapped by the dogs in an area which made movement difficult, the humans moved in to finish the prey animal off using spears. In this manner, after the dog was domesticated, humans were able to bring down huge animals like wooly mammoths, elk, moose, and the like.
Anyway, this particular gene was selected by evolution at some point during the development of the wolf. Later it became irrelevant, but it did not harm the ability of the animal to reproduce. Thus, the gene persists at least in some dogs. It is not being selected for anymore, but neither is it being selected against. Thus, Diogee has the trait, but Napoleon does not.
In The Moral Animal, Wright investigates the role of evolution in the development of human sexuality and marital relationships. One phenomenon which is pretty much universal is the so-called “Maddona-Whore Dichotomy”. That is, men tend to sort women into two sets: Those who are appropriate for casual sex and those you marry. The difference is the sexual promiscuity and libido of the woman involved. In terms of long-term relationships, as Wright amply demostrates, men actually prefer women who are relatively non-sexual, and have to be wooed and coaxed into having sex. Why? Simple. Human beings are a type of species referred to as having high “male parental investment” (MPI). Thus, a man is driven by his genes to foster the success of his offspring, and will expend a great deal of effort doing so. This is true in pretty much every human culture in the history of the world.
This is in turn driven by the nature of the human species itself: Our babies are born at a very early stage of development relative to other primates. Bonobos infants are capable of clinging to their mothers from birth, an essential trait given that bonobos monkees live in the canopies of trees. With humans, the female is typically completely devoted to the care of the infant for at least three to four years after birth. In order for this to be feasible, the father really needs to hang around and provide food, protection, shelter, etc.
In the sexual dynamic, the interests of the female and the male are in conflict: The female’s interest is to attract a male to invest in her offspring. The male’s interest is to avoid having the female mate with any other males, as that would make his investment worthless, in terms of expressing his genes. Thus, the value of virginity in females is a virtually universal human trait. The effect of cheating is different for each gender: For a male, a cheating wife is devastating: He can no longer ensure that the offspring will be his. Hence the extreme response of human males to infedility which can, and does, include violence. Female response to male infedility is very different: What threatens the female is not sexual infidelity. A bit of casual sex can be tolerated, and almost always is in many cultures. The threat to the female is emotional infidelity, because it threatens the male’s continued investment in her offspring. If the male becomes emotionally bonded to another female, he may abandon her for another family. This can, and often does, happen even in very primitive cultures. Hence the classic stereotype of jilted females sitting around commiserating about their unfaithful husbands and concluding that all men are scum.
The difference in libido is dramatic as well: Male humans have an insatiable sexual appetite compared to females. Why? Because for a male the mating opportunity presents another chance to spread those genes! A male human can mate hundreds of times a year, assuming he can get enough females to cooperate. This has actually happened in very polygamous ancient cultures like Judaism where kings like Solomon had so many wives and concubines that he could have sex with a different woman every night of his life, and not repeat for years (and possibly never repeat at all, given the acquisition of new wives and concubines!). On the other hand, a female can only reproduce about once per year (and that’s pretty aggressive), given the huge investment required by the female to bear and rear the child. Thus, once a female has mated once in a year, that’s good enough. She would rather find something to eat or catch a nap. Reproduction is not that important to her, as long as she can find a male to mate with often enough, and that does not need to be very often. The way females ovulate is very telling: Other primates have an explicit form of ovulation so that all males around her will know that she is fertile. Human females have no such cues. In biology, this is referred to as obscure ovulation. This means that the female is able to mate pretty much anytime, neatly fitting into the massive sex drive of the male. Since the male cannot tell if the female is fertile, he happily has sex with her, in the hope (at least in evolutionary terms) that she might be fertile. In the process, the emotional component of sexual love is enhanced, further ensuring the male’s parental investment.
You get the idea. Many of the characteristics which define us as a species can be explained quite well in evolutionary, Darwinian terms. I find this enchanting.