The study of changes in the social organization of maize preparation provides an important opportunity to examine the integration of households into larger systems of social and economic relationships. Spatial analysis of the distribution of manos and metates at Otumba demonstrates a change in maize production from individual, household based to a more specialized system. It is hypothesized that scarcity of firewood for cooking was a causal factor for this change, but more evidence is needed to test this idea.