“Cultural evolution can proceed so quickly because it operates, as biological evolution does not, in the "Lamarckian" mode - by the inheritance of acquired characters. Whatever one generation learns, it can pass to the next by writing, instruction, inculcation, ritual, tradition, and a host of methods that humans have developed to assure continuity in culture. Darwinian evolution, on the other hand, is an indirect process: genetic variation must first be available to construct an advantageous feature, and natural selection must then preserve it. Since genetic variation arises at random, not preferentially directed toward advantageous features, the Darwinian process works slowly. Cultural evolution is not only rapid; it is also readily reversible because its products are not coded in our genes.”