Nettie Maria Stevens: Celebrating the Work of a Remarkable Geneticist
Image of “Nettie Stevens with microscope, 1909" via Bryn Mawr College Photo Archives, BMC-Photo Archives, Series I, PA_Stevens_Nettie_005, Bryn Mawr College Special Collections.
Overlooked during her lifetime, Dr. Stevens’s impact stands the test of time
When Nettie Maria Stevens, MA, PhD died of breast cancer in 1912, she was eulogized by future Nobelist, Thomas Hunt Morgan, in the Science journal. Her passing also was noted by the New York Times. Two years prior, she had been named among the 1,000 leading American “men of science.” And prior to that, she received the Ellen Richards prize for her paper detailing her study of germ cells.
But, like many women in science at Dr. Stevens’s time, none of these accomplishments came easily and her groundbreaking work was mostly dismissed until well after her death. In Morgan’s own words, Dr. Stevens’s work was “at times wanting in that sort of inspiration that utilizes the plain fact of discovery for wider vision.” Ironically, Morgan would go on to be seen by his peers as much more cautious and ‘wanting of inspiration’ than Dr. Stevens.
Dr. Stevens’s life work centered around the collection of evidence affirming that chromosomes play a role in determining sex during development—a notion that ran afoul of more accepted theories, such as sex being determined internally, by the egg, or through external factors. This led to Dr. Stevens’s findings being both ignored and then ultimately overshadowed by the more established researcher, Edmund Wilson, who had made a similar discovery. Some assumed, erroneously, that Dr. Stevens was Wilson’s assistant, and many textbooks gave Wilson sole credit for the breakthrough, even though his conclusions were not as accurate as Stevens’s.
Adding insult to injury, in 1906, both Morgan and Wilson were invited to present their theories on sex determination at a conference. Dr. Stevens was not included. Still, this remarkable woman scientist pushed forward, making the improbable leap from data collection to the male-dominated world of interpretation.
A Deeper Look at the Science
Dr. Stevens began her research journey studying aphids, but it was really her study of mealworms that led to a breakthrough. She discovered that mealworm spermatozoa had a smaller chromosome than that of females and, when comparing progeny, it became obvious that males always received that smaller chromosome. In a paper titled “Studies on Spermatogenesis,” submitted to the Carnegie Institution and later published, Dr. Stevens detailed her research. Wilson published a similar paper the same year, but used an organism with one chromosome, which represented a different model of heredity. In the end, it was Stevens’s model that better explained the connection between genetics and sex determination.
The Life of Nettie Maria Stevens
Born in Cavendish, Vermont in 1861, Dr. Stevens’s education and career trajectory were quite impressive, especially during a time when doors were often closed to women in science. At the age of 19, Dr. Stevens graduated top of her class from Westford Academy and stayed to teach before enrolling at Westfield Normal (a teaching college). At 35, she earned both a BA and MA from Stanford University, before going on to receive a PhD at Bryn Mawr College four years later.
Though ultimately realizing her love of research ran deeper than that of teaching, she never lost the teaching instinct. In response to a hesitant student, Dr. Stevens once said, "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."
Fortunately, Dr. Stevens’s prescient comment came to fruition and, despite the lack of recognition during her lifetime, she spent the rest of her life revolutionizing the field of genetics.
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