The idea of a "meme" -- a behavior that is transmitted, like a virus, by imitation, and evolves by some analog of natural selection -- raises an obvious question: Most viruses are parasites, hostile life forms that destroy their host in reproducing themselves, so shouldn't we also expect our cultural inheritance to consist, mostly, of contagious forms of mental illness?
Viruses fit the role of pathogen because they are small, and numerous, and short-lived. Similarly, our opportunities to imitate are far more frequent than our opportunities to have children, so memes, too, have the advantage in their evolutionary arms race with us and therefore tend to be parasitic.
There are behaviors, like smoking, that fit this analysis perfectly. But it's hard to believe that it describes human culture in general. Smoking has become less popular, not more, which is proof that somehow we must have dealt with this problem in order to become what we are. But how?
Well, how do we deal with a virus? Large organisms like humans only became possible when they evolved immune systems. Similarly, elaborate culture of a modern human kind seems to require the existence of some mechanism for filtering out bad behaviors. In its absence, environmental change, errors in transmission, and the potential for maladaptive innovations would apparently make it unsafe to conserve cultural practices for more than a few generations.1 2 This may explain the very leaky transmission process we find in chimpanzees, who must continually reinvent their culture, because they're so good at forgetting it.
Rousseau saw the need to coordinate our activities in the face of temptation as the central problem of human sociality. If everyone might benefit by hunting a stag together, but we're not sure we can trust others to do their part, and we can ensure a somewhat smaller payoff by abandoning our posts to hunt rabbits, then what prevents us from all running off to chase rabbits? We must consent to a social contract and collectively punish those who fail to do their part in hunting stag.
But now another problem had to be solved, as well, or the solution to the first problem would have become a fatal trap. Once we've captured all the stags in the neighborhood and continuing to hunt them is a waste of everyone's time, but by convention we collectively punish anyone who sneaks off to hunt rabbits, which now is the only sensible thing to do, how do we abandon the convention? For it to be safe for us to have cultural conventions at all, we must have a convention about how conventions can be abandoned.
A single individual can quit smoking on his own, but our collaborative activities must be abandoned in a coordinated way. The easiest way to accomplish this is through an explicit declaration by a coordinating authority. (It helps if you've evolved a language that allows you to describe the practice you want to discourage.) Someone must declare that the era of hunting stags is now over.
With the appearance of these sorts of judges, a very human division of cognitive labor would have been established for the first time. Groups of people, or individuals, began discouraging certain behaviors and encouraging new ones.
The archaeological record shows that this change in human history coincided with the emergence of a more elaborate, less chimpanzee-like material culture, with humans now surviving, as elephants do, well after the end of the reproductive phase. Among elephants, the survival of calves is positively correlated with the age of the oldest member of the group -- she has survived droughts and knows where the water is. Humans, I think, survive past reproductive age for a rather different reason. Imitation alone isn't sufficient for the evolutionary maintenance of a human kind of culture, because there is no easy way for it to bring about the coordinated abandonment of maladaptive conventions. Instead, humans evolved more cognitively demanding transmission mechanisms -- teaching, parenting, judging, discussing -- allowing some to concentrate on imitation or innovation while others pick and choose, among the behaviors thus produced, those their age and experience allow them to recognize as desirable.
Iterated over long periods of time, this amounts to a sort of domestication of human culture. Darwin argued that domestic animals are the consequence of "a form of Selection, which may be called Unconscious, and which results from every one trying to possess and breed from the best individual animals," with "no wish or expectation of permanently altering the breed. Nevertheless we may infer that this process, continued during centuries, would improve and modify any breed..." Many modern institutions -- schools, courts, legislatures -- act like cultural adaptations for carrying on exactly this sort of artificial selection, places where the meanings of words, or cultural norms, or useful skills are repeatedly subjected to a recursive filtration process, in which the results of this generation become the filter for the next.
So does this mean we can stop worrying about contagious forms of mental illness and bad behavior? Not exactly, any more than the existence of an immune system means we can stop worrying about the flu. Because the main selective force on the pathogen is the defenses the host has evolved against it, the virus becomes a sort of negative image of those defenses, becoming perfectly optimized to slip through the cracks. In the same way, human culture probably has a tendency to evolve into whatever would fool parents and teachers and voters and judges. Guilt, envy, our love of beauty, our infatuation with the rational -- any weakness will be exploited in the interests of the meme. The better our defenses get, the cleverer these deceptions should become, which is why the most dangerous kinds of folly always come from the wise, and why we must remain vigilant in order to defend against them.
1. Rogers, A. (1988) Does biology constrain culture? American Anthropologist
2. Enquist, M., Ghirlanda, S. (2007) Evolution of social learning does not explain the origin of human cumulative culture. Journal of Theoretical Biology 246, 129-35.