In the early 70s, Howard Pattee (e.g., 1972, 1973) argued that modem evolutionary theory is incomplete. Since the 1930s, "evolutionary theory" has become identical with Neo-Darwinism (cf. Mayr & Provine, 1980) which focuses on populations of conspecifics. These often relatively small and isolated populations explore the "fitness landscape" through mutations in their DNA (variation), enhancing or endangering their survival (selection). Although the value of Neo-Darwinism is beyond dispute, Pattee has made clear that the search space is often too large to allow a population to reach workable solutions to its problems. Unless, he argued, the search space is constrained by natural self-simplification.