Making blood 'Melanesian': fieldwork and isolating techniques in genetic epidemiology (1963-1976)

'Isolated' populations did not exist unproblematically for life scientists to study. This article examines the practical and conceptual labour, and the historical contingencies that rendered populations legible as 'isolates' for population geneticists. Though a standard historiographical narrative tells us that population geneticists were moving from typological understandings of biological variation to processual ones, cultural variation was understood as vulnerable to homogenisation. I chart the importance that D. Carleton Gajdusek placed on isolates from his promotion of genetic epidemiology in WHO technical reports and at a Cold Spring Harbour symposium to his fieldwork routines and collection practices in a group of South Pacific islands. His fieldwork techniques combined social, cultural and historical knowledge of the research subjects in order to isolate biological descent using genealogies. Having isolated a population, Gajdusek incorporated biological materials derived from that population into broad categories of 'Melanesian' and 'race' to generate statements about the genetics of abnormal haemoglobins and malaria. Alongside an analysis of Gajdusek's practices, I present different narratives of descent, kinship and identities learned during my ethnographic work in Vanuatu. These alternatives show tacit decisions made pertaining to scale in the production of 'isolates'.