Historiography on tropical medicine and determinist ideas about climate and racial difference rightly focuses on links with nineteenth- and twentieth-century colonial rule. Occasionally and counterintuitively, however, these ideas have been redeployed as anticolonial argument. This article looks at one such instance; the racial physiology of Indian economist, ecologist, and anticolonial nationalist Radhakamal Mukerjee (1889–1968). It argues that the explanatory context was mid-twentieth-century discussion of global population growth, which raised questions of density and belonging to land. Ecology offered a new language and scientific system within which people and place were conceptually integrated, in this instance to anticolonial ends.