Nettie Stevens
Nettie Maria Stevens (July 7,1861 - May 4,1912) was an early American geneticist. She and Edmund Beecher Wilson were the first researchers to describe the chromosomal basis of sex.
An outstanding student, Nettie Stevens completed in two years the four-year course at Westfield Normal School (now Westfield State College) in Massachusetts. She graduated at the top of her class. At Stanford, she received her B.A. in 1899 and her M.A. in 1900. Stevens continued her studies in cytology at Bryn Mawr, where she was influenced by the work of the previous head of the Biology Department, Edmund Beecher Wilson, and by that of his successor, T. H. Morgan.
Stevens was one of the first American women to be recognized for her contribution to science. Her research was done in Bryn Mawr College. She discovered that chromosomes determine sex, i.e. if a baby is male or female. This work was done in 1905. The experiments done to determine this used a range of insects, she identified the Y chromosome in the mealworm Tenebrio. She deduced the chromosomal basis of sex depended on the presence or absence of the Y chromosome. She did not start her research until her thirties and completed her PhD in 1903. She successfully expanded the fields of embryology and cytogenetics. She died on May 4,1912 of breast cancer.
Quotes
"Modern cytological work involves an intricacy of detail, the significance of which can be appreciated by the specialist alone; but Miss Stevens had a share in a discovery of importance, and her work will be remembered for this, when the minutiae of detailed investigations that she carried out have become incorporated in the general body of the subject. " — Thomas Hunt Morgan, following Stevens' death in 1912.