Nettie Maria Stevens

Time Period


Subject Categories

Education, Science / Engineering

Notable Facts

A biologist and geneticist whose work helped illustrate that a particular chromosome determined the sex of an organism.

Personal Information

Date of Birth


Date of Death


Primary Residence


Historical Significance

Nettie Maria Stevens was born in Cavendish, Vermont on July 7, 1861. Nettie and her sister Emma Julia (born January 14, 1863) were the surviving offspring of Ephraim Stevens and Julia Adams. In 1863, Stevens' mother died. Two years later her father married Ellen C. Thompson, a native of West Haven, Vermont, and the family moved to the Forge Village section of Westford, Massachusetts.

Ephraim Stevens worked as a carpenter. He was considered successful enough for the time to provide his daughters with the best education then possible. Stevens' early education took place in the Westford public schools, where her ability as a student was noted in school records, along with a perfect attendance record. After public school, Stevens attended Westford Academy, graduating in 1880. According to Westford Academy school records, only 11 students graduated in the years between 1872-1883, and only three were women: Stevens, her sister Emma, and one other.

Before beginning college work, Stevens taught Latin, English, math, physiology, and zoology at a Lebanon, New Hampshire high school for three terms.

Then she entered the Westfield Normal School in Westfield, Massachusetts (now Westfield State College) where she was an outstanding student who appears to have completed four years of study in only two.

Over the next 13 years Stevens worked as a librarian, a schoolteacher and a principal's assistant. During this period her family would move from Westford to her father's hometown of Chelmsford, Massachusetts.

In 1896, at the age of 35, Stevens left New England. She enrolled at Stanford University in Palo Alto, California as a physiology major. Over summer breaks Stevens worked at the Hopkins Seaside Laboratory in Pacific Grove, California. Here she studied histology (the microscopic structure of organic tissues) and cytology (the microscopic appearance of cells). Stevens received her bachelor's degree in 1899, but stayed at Stanford working on her master's thesis. In 1900 published her first paper on microbiology called, " Studies on Ciliate Infusoria."

After receiving her Master's Degree, Stevens returned east to study at Bryn Mawr College. The prestigious women's liberal arts school was at the time only 15 years old and was the only institution then offering graduate degrees and doctorates to women. The college had previously employed the prominent biologists Edmund Beecher Wilson and Thomas Hunt Morgan who shared research specialties with Stevens and would later become both her mentors and her rivals. During her time at Bryn Mawr, Stevens so excelled that she was awarded a fellowship to study abroad in Italy and Germany. In 1903, Bryn Mawr awarded Stevens a PhD.

In 1905, Stevens received a grant from the Carnegie Institution, which freed her financially and allowed her to devote herself to research. But Stevens remained connected with Bryn Mawr. From 1903 until her death nine years later, Stevens held the successive titles of Research Fellow in Biology, Reader in Experimental Morphology, and Associate in Experimental Morphology. The Bryn Mawr Trustees eventually created a research professorship especially for her, but by then she was already suffering from terminal breast cancer. Stevens died on May 4, 1912.

Nettie Stevens was one of the first female scientists in America to be recognized for her contribution to science. Her important work was in the field of cytogenetics (the branch of genetics dealing with the cellular components, particularly chromosomes, associated with heredity.) In a 1905 study of mealworms, she identified the Y chromosome and hypothesized that sex determination was dependent on the presence or absence of the Y chromosome.

Following her death, her previous teacher, Thomas Hunt Morgan, publicly dismissed Stevens, suggesting she was more of a researcher than a scientist. Credit for discovering the chromosomal basis for sex determination is generally given to Edmund Beecher Wilson, who was doing similar research independently at Columbia University, but who had read Stevens’ theories before publishing his own. For their work in genetics, Hunt and Wilson were awarded the Nobel Prize in Physiology or Medicine in 1933.


  • Biologist
  • Cytogeneticist
  • Schoolteacher
  • Librarian
  • Research Fellow in Biology (Bryn Mawr 1903-1904)
  • Reader in Experimental Morphology (Bryn Mawr 1904-1905)
  • Associate in Experimental Morphology (Bryn Mawr 1905-1912)


  • Westfield Normal School (now Westfield State College)
  • Stanford University: B.A. 1899
  • M.A. 1900
  • Bryn Mawr: PhD 1903

Additional Information (Bibliography)

  • Ogilvive, M.B. and C. J. Choquette. "Nettie Maria Stevens (1861-1912): Her Life and Contributions to Cytogenetics." Proceedings of the American Philosophical Society, Vol. 125, No. 4, (Aug. 21, 1981), pp. 292-311 Link

Additional Images

Stevens, Nettie