Social science has long fought shy of the natural sciences. Meanwhile, concerns with the environment, health and the new genetics are creating a need for systematic links to be made between these disciplines. This paper suggests a new way in which social theory can be linked to biology. Recent developments in biology point to the importance of considering organisms in relation to their environment. And work in epidemiology stresses the links between the infant-development, health in later life and the well-being of future generations. Complex combinations of genetically-determined predispositions and capitalist social relations are responsible for important features of contemporary social stratification and well-being. The paper is informed by critical realist epistemology and Marx's theory of the subsumption. Such a fusion leads to a key assertion. Capital tends to modify the powers of human biology in its own image.