Revolution" which are still used today in the branch of pre-historic anthropology. In 1941 anthropologist Robert Redfield wrote about a shift from 'folk society' to 'urban society'. By the 1940s cultural anthropologists such as Leslie White and Julian Steward sought to revive an evolutionary model on a more scientific basis, and succeeded in establishing an approach known as neoevolutionism. White rejected the opposition between "primitive" and "modern" societies but did argue that societies could be distinguished based on the amount of energy they harnessed, and that increased energy allowed for greater social differentiation (White's law). Steward on the other hand rejected the 19th-century notion of progress, and instead called attention to the Darwinian notion of "adaptation", arguing that all societies had to adapt to their environment in some way. The anthropologists Marshall Sahlins and Elman Service prepared an edited volume, Evolution and Culture, in which they attempted to synthesise White's and Steward's approaches. Other anthropologists, building on or responding to work by White and Steward, developed theories of cultural ecology and ecological anthropology. The most prominent examples are Peter Vayda and Roy Rappaport. By the late 1950s, students of Steward such as Eric Wolf and Sidney Mintz turned away from cultural ecology to Marxism, World Systems Theory, Dependency theory and Marvin Harris's Cultural materialism. Today most anthropologists reject 19th-century notions of progress and the three assumptions of unilineal evolution. Following Steward, they take seriously the relationship between a culture and its environment to explain different aspects of a culture. But most modern cultural anthropologists have adopted a general systems approach, examining cultures as emergent systems and arguing that one must consider the whole social environment, which includes political and economic relations among cultures. As a result of simplistic notions of "progressive evolution", more modern, complex cultural evolution theories (such as Dual Inheritance Theory, discussed below) receive little attention in the social sciences, having given way in some cases to a series of more humanist approaches. Some reject the entirety of evolutionary thinking and look instead at historical contingencies, contacts with other cultures, and the operation of cultural symbol systems. In the area of development studies, authors such as Amartya Sen have developed an understanding of 'development' and 'human flourishing' that also question more simplistic notions of progress, while retaining much of their original inspiration. Neoevolutionism Neoevolutionism was the first in a series of modern multilineal evolution theories. It emerged in