At the present time there is hardly any question in biology of more importance than this of the nature and causes of variability (Charles Darwin, 1880) 2 In cultural studies biology tends to be viewed as deterministic, bearing little relation to environmental factors. In this article I argue that this was not necessarily so for the Victorians, but that reductive thought and practice which emphasised determinism developed in the second half of the nineteenth century in response to a number of social and scientific factors. Separating organism from environment, it focused on a biology divorced from social and historical context and was informed by rising concern over urban poverty, degeneration, and imperial rivalries and by a newly professionalised and institutionalised science. I argue that in rejecting biology as deterministic and emphasising fluidity, postgenomic biology recapitulates a Victorian insight.Reductionism in science, much like reductionism outside science, simplifies.It can be ontological, epistemological, and methodological. In science it is often a powerful and necessary method which seeks to isolate and control phenomena in order to explain them.3 But it can fall into ideology, especially in the context of human behaviour. Stumbling at complexity, it may seek to explain higher-level processes (e.g., adaptation, adultery or addiction) by lower-level processes (e.g. heredity, molecular biology, genes), or seek to bring essentialist concepts (e.g. biological sex) to indeterminate social processes (e.g. map reading). 4 Reductionism, as method or as ideology, and sometimes as both, seeks to explain the complex, the whole, or the interactive or dynamic according to the simple, the part, or the linear or unidirectional. Reductionism is usually deterministic, allowing little possibility for individual agency or choice. Where, exceptionally, determinism acknowledges complexity, or competing or converging causes, and does not seek to explain the higher by lower, complex by simple, it is not inherently reductive. In The Disorder of Things (1993) John Dupré observes the connections between reductionism, determinism and essentialism as the three pillars of conventional classification,
