One of the basic lessons learned in science classrooms around the world is the sex chromosome determination system , which in the human species and many other animals is given by the X and Y sex chromosomes. In these classrooms too It is learned that Thomas H. Morgan received the 1933 Nobel Prize in Physiology and Medicine for his crucial contributions in demonstrating this theory. What, at least until now, does not appear in many textbooks, is that the works of Nettie Marie Stevens (1861-1912) were crucial to reach this knowledge.
Perhaps it is because, for many centuries, the role of women in science has received much less attention than that of their male colleagues, or because Stevens’ scientific career was very short, the truth is that his contributions to genetics are quite unknown to the general public.
Nettie Marie Stevens served as a teacher and librarian for much of her life, and it was not until 1900 that she was accepted to Bryn Mawr College (Pasadena, California), where she obtained her doctorate at the age of 42. Breast cancer took his life when he was 51 years old, so his scientific career was quite short. However, in that short time, Stevens wrote several books, received numerous awards and scholarships, and published a study that revolutionized the understanding of hereditary sex determination at the time.
Works with Thomas H. Morgan
During his stay at Bryn Mawr College he met Thomas Morgan and maintained a close professional relationship with him. In a letter of recommendation written by Morgan to support Stevens’s application for a scholarship at the Carnegie Institution of Washington, the biologist referred to her thus: none more capable and independent in research work than Miss Stevens, and now that she has her degree she is dedicating all her work to research. Miss Stevens is not only prepared, but also possesses the natural talent that I think is much more difficult to find. He has an independent and original mind and does anything he wants from start to finish ”.
Stevens’ discoveries regarding the chromosomal inheritance of sex are due to his work observing the sex cells of aphids and beetles under the microscope. Specifically, the study of the flour beetle ( Tenebrio molitor ) led him to locate a pair of chromosomes of different sizes, which separated during meiosis and originated two types of sperm. For the first time, it was considered that it was two chromosomes, and not just one, that were related to the determination of sex.
Nettie Marie Stevens died long before Morgan’s discoveries were publicly recognized , and we do not know if she shared the Nobel Prize with him, but in any case it seems fair that the history of science should pay her the tribute she deserves for her contributions to world of genetics.
