1861-1912

American Cytogeneticist

Nettie Stevens hypothesized that chromosomes in sperm determine the gender of embryos when fertilization of an egg occurs. Her research confirmed scientific speculation based on Gregor Mendel's nineteenth-century genetic experimentation showing that traits such as the sex of offspring are inherited from parents. Stevens proved her theory by researching insects and showing that chromosomes specified whether embryos were male or female. Although scientists at the time were skeptical of her findings, eventually her concept became a foundation of modern genetic knowledge.

Born in Cavendish, Vermont, Stevens was the daughter of Ephraim and Julia (Adams) Stevens. She grew up in Westford, Massachusetts, where she attended public schools and graduated from Westford Academy. Stevens taught high school classes in zoology, physiology, and Latin in New Hampshire before returning to Westford, where she was a teacher at her alma mater and a public librarian...