Women helped build China's 2,200-year-old Terracotta Warriors, according to a new study of fingerprints preserved in the clay warriors - the first quantitative biological evidence challenging the long-standing assumption that the standardized, large-scale production of the life-size clay figures was exclusively men's work. Researchers from the Emperor Qinshihuang's Mausoleum Site Museum and Shandong University examined 79 distinct fingerprints on 23 terracotta figures. Using a Bayesian mixture model - a statistical method that estimates the overall makeup of a group from imperfect individual clues rather than identifying any single person - they concluded that about 45% of the prints likely came from adult men, 32.7% from adult women, while 22.3% from people under age 15.