Shape Variability and Classification of Human Hair: A Worldwide Approach

The study aimed to develop a more scientific and factual approach to classifying human hair based on physical features rather than traditional ethnic categories. Researchers analyzed hair from 1,442 subjects across 18 countries, using three descriptors: curve diameter (CD), curl index (i), and number of waves (w). This method resulted in a classification system with eight well-defined hair categories, providing a more objective and reliable standard for use in cosmetic and forensic sciences. The new classification also aimed to explore whether hair shape diversity aligns with continuous geographic and historical patterns of human genetic variation or shows significant discontinuities between large human subdivisions.