Nettie Maria Stevens was born July 7, 1861, in Cavendish, Vermont, to a middle-class family. Growing up in post-Civil War America, there was little professional opportunity available to women, beyond teaching, nursing, or secretarial work. Despite that, Nettie was determined to carve her own path… she wanted to be a scientist.

While she did wind up working as a teacher and librarian for nearly sixteen years, it was only a means to an end… a way to save up enough money to attend Stanford University, one of the only universities that accepted women at the time. Nonetheless, her enthusiasm for science made her a caring and dedicated teacher.

“How could you think your questions would bother me? They never will, so long as I keep my enthusiasm for biology; and that, I hope will be as long as I live.” – Nettie to a student

In 1896, with enough money socked away in the bank, Nettie, then 35 years old, enrolled at Stanford, and graduated four years later. Reportedly an exceptionally bright student, she went on to earn her master’s degree from Bryn Mawr College in 1900 and then her PhD in 1903.

Finally, at age 39, Nettie’s dream was on its way to becoming reality when she began working as a research scientist. The next 11 years would be the most productive of her life.

nettie stevens_1909 Naples, ItalyDuring a fellowship abroad in Naples, Italy, Nettie became interested in chromosomes and the process of sex determination. When she returned to the Unites States, she won a grant from the Carnegie Institute and used it to conduct studies on the chromosomes of mealworms and other insects. What she discovered was that the males made reproductive cells with both X and Y chromosomes whereas the females made only those with X. She concluded that sex is inherited as a chromosomal factor and that males determine the gender of the offspring.

Another researcher, Edmund Wilson, made a similar discovery at about the same time, but Nettie is generally considered to have made the larger theoretical leap (one which was ultimately proven correct).

Nettie Maria Stevens continued to do research and teach at Bryn Mawr and Cold Spring Harbor Laboratories until her death from breast cancer on May 4, 1912.

In just eleven short years working as a scientist, this Woman You Should Know managed to contribute more to her field than many scientists have with much longer careers.

Source: Library of Congress – Notable Women In Science Knowledge Cards, Authored & Created By Aimee Hess; Scitable

Over 100 Years After Nettie’s Discovery…