This article gives an overview of the visual culture shared by a number of scientists studying human variation in the first half of the 20th century. This was a time when most scientists shared the conceptual and terminological framework of ‘racial classifications’ to capture the structure of human variation. Clearly, drawings – and later photographs – of people from all over the world constituted a crucial part of the well-established visual culture concerned with human variation. The article, however, focuses on (...) the representational tools for visualizing aspects of human variation that were not so obvious to the eye of the observer. It contextualizes researchers’ strategies of visualizing human diversity within the pictorial traditions of relevant fields, particularly physical anthropology and human genetics. Starting from 1900, the article demonstrates how scientists built up a rich visual repertoire for understanding human diversity, one that integrated maps, tables, photos, drawings, diagrams, family and phylogenetic trees. The representations included abstract and non-abstract elements, but increasingly rested on diagrammatic visualizations. Notably, although these diagrammatic visualizations grew in sophistication and methodological rigor, they were rarely used in academic textbooks. More often, mixed strategies of visualizations – diagrammatic elements integrated into non-diagrammatic images – were chosen as representations for human diversity. In the postwar period, most of those visualizations disappeared from scientific publications, but not from popular media. For the scientific publications, one can argue that a number of scientists paid specific attention to visualizations and their deterministic potential. Some argued that particularly maps and trees were altogether problematic in their visualization of human evolution and human diversity. Others sought out new and better ways of constructing trees and maps to visualize truth-claims about human diversity. Here, diagrammatic elements played a key role. Notably, researchers who employed typological approaches for physical anthropology, and who admitted that there was a moment of intuition in their practices, aspired to meet the demands of mechanical objectivity by establishing abstract inscriptions of their typological assessments. (shrink)