The Durkheimian concept of the density of social relationships may prove more fruitful than the historical materialist notion of a social hierarchy for thinking about the social location of epistemic agents in science. To define a scientist's social location in terms of the density of her professional relationships with other scientists permits us to give a more precise characterization of marginalization and thus to formulate more testable hypotheses about marginalized groups in science. The notion of social density helps to explain not only how some individual scientists are more likely than others to get a hearing for their ideas, but also how scientific inquiry flourishes more in some societies than in others.