There is an assumption prevalent in current Western political thought that Marxist theory has been discredited by collapse of communism, and that a capitalist, free market theory is the only viable one. It is argued here that the interplay of power and cooperation in society can best be understood by combining insights from both paradigms. The argument is illustrated with material from the French village of Pellaport and neighbouring communities, which I first studied for my PhD in 1969 and have most recently re-studied during the summer of 1995. Darwinian theory owes much to the model of market economics and, in some regards, Darwin’s theory of evolution can be considered an application of free market principles to nature, subsequently reapplied to social behaviour by socioecologists. The chapter will consider how adaptationist models of social process derived from Darwinian theory can elucidate one of the key defects of Marx’s theory. It will, however, also argue that some of Marx’s principles must be retained, not only to explain how social adaptations can result in imbalances in the distribution of power, but also to explain why social change sometimes seems to proceed in the linear, cumulative fashion often referred to as ‘progress’, which plays no part in Darwinian theory.