 Boyd and Henrich acknowledge that this does not make population-level distributions perfectly reliably inherited. But this does not show that cumulative evolution acting on cultural inheritance is impossible. At the genetic level, highly faithful copying processes allow even very small selective forces to preserve adaptive variation. Less faithful copying demands stronger selective forces if adaptive variation is not to be lost. Boyd and Henrich are confident that selective forces in the cultural realm are stronger than selective forces in the genetic realm. The moral, once again, is that it is important not to focus too closely on genetic evolution as a model for cultural evolution.