Nettie Stevens...

· In the early 1900s, Nettie Stevens quietly upended what science thought it knew about how life begins. Working in a time when women in laboratories were rare, she studied mealworms under her microscope and noticed something extraordinary—males had one large chromosome and one smaller one, while females had two large chromosomes. It was a meticulous, painstaking observation, but it unlocked a truth no one had proven before: sex was determined by specific chromosomes, later named X and Y. Her discovery should have been a career-defining triumph. Instead, much of the recognition went to her male colleague, Thomas Hunt Morgan, whose reputation and influence in the scientific community helped overshadow her work. Stevens, who had trained relentlessly and built her research from the ground up, was left on the margins of her own achievement. She never lived to see her name fully restored to the discovery—she died of breast cancer at just 50—but her findings remain one of the most important milestones in genetics. Even if history tried to tuck her away in a footnote, her work still reshaped how we understand life itself. And that is a legacy no one can erase. --- From "She's So Cool".