Nettie Stevens
Nettie Stevens was an American geneticist born in 1861 in Cavendish, Vermont who made significant contributions to the field of biology through her discovery that an organism's sex is determined by its chromosomes. Prior to her discovery, scientists believed that sex depended on factors such as temperature in the environment or a woman’s diet during pregnancy. Stevens opposed this idea widely thought to be true through her revolutionary report— ‘Studies in Spermatogenesis’.
Societal norms that made it difficult for women to pursue higher education affected Stevens’s desire to work in the scientific field professionally. She worked as a high school teacher and librarian for over a decade after graduating high school to earn a living before deciding to enroll at Stanford University in 1896, at the age of 35, after she had saved enough to do so. She then went on to earn her Bachelor’s in Physiology in 1899 and Master’s in Biology in 1900, and by the time she had finished it, she feared that she would be forced to return to her profession as a teacher due to financial struggles. However, she was able to go further to complete her Ph.D. at Bryn Mawr College, Bryn Mawr, Pennsylvania in 1903 after she was awarded the Carnegie Institution Grant #177 for her skill, which took the weight of the financial burden of her shoulders.
Stevens began her research professionally at 39, and conducted cellular experiments through the analysis of reproductive habits of insects and mealworms. She studies the process of spermatogenesis and its outcomes. She compared her observation in the organisms with physical traits in the offspring by counting individual chromosomes inside both the male sperm cells and female egg cells of the organisms. She published the first part of her paper— ‘Studies in Spermatogenesis’ in 1905 and the second part in 1906 which covered her discoveries: the existence of X and Y chromosomes, the genetic link to physical traits, and that male sperm determines the sex of offspring.
Nettie Stevens passed away in 1912 at the age of 50, leaving behind a legacy of scientific brilliance.
