Meet Nettie Stevens: The Genetics Pioneer Who Discovered That Sex Is Determined By Chromosomes

Born 155 years ago today in Vermont, biologist Nettie Stevens was a pioneer in modern genetics and an activist who sought to bring female scientists to the forefront.

At the age of 35, Stevens enrolled at Stanford University where she spent many summers pursuing her passion for biology. Despite how uncommon it was for women at the time, she continued her education at Stanford to earn her master's degree in 1900 and later her doctorate at Bryn Mawr College in Pennsylvania.

Among some of her many successes was her continued study of what Gregor Mendel already established as the rules of heredity.

"We find that the evidence is overwhelmingly on the side of the view that sex is determined in the egg; but to the question of how sex is determined in the egg, no thoroughly convincing answer has yet been given," Stevens wrote in an essay in 1905, eventually concluding in reports that sex is, in fact, determined by chromosomes.

Unfortunately, at the same time, America's first cell biologist and Columbia University's Edmund Beecher Wilson independently made the same discovery.

"It is generally stated that E. B. Wilson obtained the same results as Stevens, at the same time," Vox quotes historian Stephen Brush from "The History of Science Society," adding that "Wilson probably did not arrive at his conclusion on sex determination until after he had seen Stevens' results... Because of Wilson's more substantial contributions in other areas, he tends to be given most of the credit for this discovery."

In the end, Stevens lost her battle with breast cancer in 1912, and because Wilson had the XY and Stevens had the XX, he, conveniently, got the credit.

See how today's Google Doodle pays tribute to her discoveries in celebration of her birthday.

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