The <scp>Trotter</scp> collection: A review of <scp>Mildred Trotter</scp>'s hair research and an update for studies of human variation

The review of Mildred Trotter's hair research and its updates emphasize the complexity and variability of hair traits across diverse populations, challenging traditional racial classifications based on hair morphology. By reanalyzing Trotter's original data with modern methods, the study confirms the reliability of her measurements and expands on her findings, revealing that hair shape, size, and medullary patterns are not reliable indicators of ancestry due to significant intra-individual and inter-population variability. The analysis of 28,404 hairs showed weak correlations between hair traits and ethnogeographic ancestry, highlighting the continuous nature of hair morphology. The study also examined melanosome distribution and found significant variation among individuals, with a weak correlation between hair traits and climate variables. Overall, the research underscores the need for precise measurement techniques and further genetic studies to understand the relationship between hair traits and genotype.