The case of the meme idea illustrates a general puzzle. Cultures do contain items — ideas, norms, tales, recipes, dances, rituals, tools, practices, and so on — that are produced again and again. These items remain self-similar over social space and time: in spite of variations, an Irish stew is an Irish stew, Little Red Riding Hood is Little Red Riding Hood and a samba is a samba. The obvious way to explain this stability at the macro level of the culture is, or so it seems, to assume fidelity at the micro level of interindividual transmission. Little Red Riding Hood must have been replicated faithfully enough most of the time for the tale to have remained self-similar over centuries of oral transmission or else the story would have drifted in all kinds of ways and the tale itself would have vanished like water in the sand. Macro stability implies micro fidelity. Right? Well, no. When we study micro processes of transmission — leaving aside those that use techniques of strict replication such as printing or internet forwarding — what we observe is a mix of preservation of the model and of construction of a version that suits the capacities and interests of the transmitter. From one version to the next, the changes may be small, but when they occur at the population scale, their cumulative effect should compromise the stability of cultural items. But — and here lies the puzzle — they don't. What, if not fidelity, explains stability?
Well, bits of culture — memes if you want to dilute the notion and call them that — remain self-similar not because they are replicated again and again but because variations that occur at almost every turn in their repeated transmission, rather than resulting in "random walks" drifting away in all directions from an initial model, tend to gravitate around cultural attractors. Ending Little Red Riding Hood when the wolf eats the child would make for a simpler story to remember, but a Happy Ending is too powerful a cultural attractor. If a person had only heard the story ending with the wolf's meal, my guess is that either she would not have retold it at all — and that is selection — , or she would have modified by reconstructing a happy ending — and this is attraction. Little Red Riding Hood has remained culturally stable not because it has been faithfully replicated all along, but because the variations present in all its versions have tended to cancel one another out.
