Profile of the Day: Nettie Stevens

On this day in 1861, American geneticist Nettie Stevens was born. A pioneer of her field, Stevens is credited with discovering sex chromosomes.

Image: Nettie Stevens / Wikimedia Commons

Stevens was born on July 7, 1961 in Cavendish, Vermont to Julia Adams and Ephraim Stevens. An excellent student, Stevens was near the top of her class. She and her sister, Emma, were two of three women to graduate from Westford Academy, a private high school, between 1872-1880. After studying at Stanford University, Stevens went on to earn her Ph.D at Bryn Mawr college in Pennsylvania.

In 1905, Stevens published her groundbreaking research on sex determination. In her study of mealworms, Stevens discovered that the males produced sperm with X and Y chromosomes while the females only produced eggs that carried X chromosomes. She deduced that the presence or absence of the Y chromosome determined sex. Unfortunately, Stevens was not immediately recognized for her groundbreaking research. That same year, researcher Edmund Wilson had also come to a similar conclusion and was often credited alone for the discovery. Because of Wilson’s reputation and substantial contributions to other areas, his findings largely overshadowed Stevens’s work. However, it was Stevens who presented the stronger, and ultimately more correct, conclusion. It was not until after her death in 1912 that Stevens was finally recognized for her groundbreaking accomplishments.

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