For generations, medicine has measured aging with a single ruler applied to all bodies equally — but a new study published in Nature Medicine suggests that men and women are running on different biological clocks. Researchers built 38 organ-specific aging models trained separately by sex, drawing on brain scans, genetic data, and decades of clinical follow-up, and found that the tissues aging fastest, and the diseases those patterns predict, differ meaningfully between males and females. The finding does not divide humanity so much as it refines our understanding of it: biological time, it tur