Nettie Stevens

Nettie Stevens
Born Nettie Maria Stevens
July 7, 1861
Cavendish, Vermont
Died May 4, 1912(1912-05-04) (aged 50)
Baltimore, Maryland
Nationality United States
Fields Genetics
Alma mater Westfield Normal School
Stanford University
Bryn Mawr College
Doctoral students Alice Middleton Boring
Known for XY sex-determination system
Influences Edmund Beecher Wilson; Thomas Hunt Morgan

Nettie Maria Stevens (July 7, 1861 – May 4, 1912) was an early American geneticist. She and Edmund Beecher Wilson (1856-1939) were the first researchers to describe the chromosomal basis of sex, but both concluded their research independently.[1]

Personal Life

Nettie Maria Stevens was born on July 7, 1861 in Cavendish, Vermont to Julia (Adams) and Ephraim Stevens. After the death of her mother, Stevens's father remarried and the family moved to Westford, Massachusetts. As an outstanding student, she graduated from Westford Academy in 1880. After teaching for three terms, she continued her education at Westfield (Massachusetts) Normal School, now Westfield State University, where she graduated with the highest scores in her class of 30.[2] She completed in two years the four-year course at Westfield Normal School.[3]

Education

Stevens taught high school and was a librarian. Her teaching duties included courses in physiology and zoology, as well as mathematics, Latin, and English. Her interest in zoology may have been influenced by taking summer courses near Martha's Vineyard in the 1890's.[4]

After she graduated top in her class, she went to Stanford, where she received her B.A. in 1899 and her M.A. in 1900. She also completed one year of graduate work in physiology under Professor Jenkins, and histology/ cytology under Professor McFarland.[5]

Stevens continued her studies in cytology at Bryn Mawr, where she was influenced by the work of the previous head of the biology department, Edmund Beecher Wilson, and by that of his successor, Thomas Hunt Morgan.[3] She also studied marine organisms in Europe, at Helgoland and Naples Zoological Station.[5][6] In her first year at Bryn Mawr, Stevens received a graduate scholarship in biology. The following year, she was named a President's European Fellow, and studied at the University of Wurzburg, Germany.[2] After receiving her Ph.D. from Bryn Mawr, Stevens was given an assistantship at the Carnegie Institute of Washington in the year 1904–1905. Several subsequent studies of germ cells in aphids appeared as a result. One paper (1905) won Stevens an award of $1,000 for the best scientific paper written by a woman. Another work, Studies in Spermatogenesis, highlighted her entry into the increasingly promising focus of sex-determination studies and chromosomal inheritance.[7] It was at this institute that Stevens got her sex determination work published as a report in 1905. At Bryn Mawr, Stevens focused on topics such as the regeneration in primitive multi cellular organisms, the structure of single cell organisms, the development of sperm and eggs, germ cells of insects, and cell division in sea urchins and worms.[7]

Career

Nettie Stevens' microscope, Bryn Mawr College

Stevens was one of the first American women to be recognized for her contribution to science. Her research was done in Bryn Mawr College. Her highest rank attained was the associate in experimental morphology (1905- 1912). She discovered that in some species chromosomes are different among the sexes, by observations of insect chromosomes. The discovery was the first time that observable differences of chromosomes could be linked to an observable difference in physical attributes, i.e. if an individual is a male or a female. This work was done in 1905. The experiments done to determine this used a range of insects. She identified the Y chromosome in the mealworm Tenebrio. She deduced the chromosomal basis of sex depended on the presence or absence of the Y chromosome. She did not start her research until her thirties and completed her PhD in 1903. She successfully expanded the fields of embryology and cytogenetics.

Stevens failed to gain a full regular university position. However, she achieved a career of research at leading marine stations and laboratories. Her record of 38 publications includes several major contributions which further the emergence of ideas of chromosomal heredity. As a result of her research, Stevens provided critical evidence for Mendelian and chromosomal theories of inheritance.[1]

Stevens worked to be able to become a full researcher at Bryn Mawr. However, before she could take the research professorship offered to her, She died on May 4, 1912 from breast cancer, at Johns Hopkins Hospital, before she was able to fully take up a new faculty position.[6]

Stevens is a somewhat controversial character. Following her death, Thomas Hunt Morgan wrote an extensive yet dismissive obituary for the journal Science,[8] implying that she was more of a technician than a scientist. This later assessment belies his earlier statement in a letter of recommendation: "Of the graduate students that I have had during the last twelve years I have had no one that was as capable and independent in research as Miss Stevens...".[9]

Stevens was the first to recognize that females have two large sex chromosomes. Wilson did not see this because he only performed tests on the testis, because eggs are too fatty for the old staining procedures. Wilson even reissued his original paper and thanked Nettie Stevens for this finding. This finding is what then allowed Wilson to combine his idea of idiochromosomes with her heterosomes. This shows that Stevens was very influential in this process. Most biology textbooks credit Morgan for mapping the first gene locations onto chromosomes of fruit flies Drosophila melanogaster, but what is often missed is that it was Stevens who brought the fruit fly into Morgan's lab in the first place.

Over her life time, she wrote about 38 papers on different subjects.[7]

Nettie Maria Stevens was buried in the Westfield, Massachusetts cemetery alongside the graves of her father, Ephraim, and her sister, Emma.[5]

Quotes

"Her single-mindedness and devotion, combined with keen powers of observation; her thoughtfulness and patience, united to a well-balanced judgment, account, in part, for her remarkable accomplishment”. - Thomas Hunt Morgan, in an obituary note following Stevens' death in 1912.[2]

Modern cytological work involves an intricacy of detail, the significance of which can be appreciated by the specialist alone; but Miss Stevens had a share in a discovery of importance, and her work will be remembered for this, when the minutiae of detailed investigations that she carried out have become incorporated in the general body of the subject.
— Thomas Hunt Morgan, following Stevens' death in 1912 (The Scientific Work of Miss N. M. Stevens. Science, Vol. 36 (No. 928), October, 1912)[3]

References

  1. 1 2 "MSU Authentication | Michigan State University". doi:10.1093/acref/97801996%20666.001.0001/acref-9780199766666-e-465.
  2. 1 2 3 "MSU Authentication | Michigan State University". doi:10.1093/acref/97801996%20666.001.0001/acref-9780199766666-e-465.
  3. 1 2 3 "Nettie Maria Stevens (1861-1912)". The Marine Biological Laboratory. Archived from the original on March 31, 2013. Retrieved August 18, 2013.
  4. ↑ Hagen, Joel. Nettie Stevens and the Problem of Sex Determination. www1.umn.edu: Minneapolis: University of Minnesota. pp. 37–47.
  5. 1 2 3 "Nettie Maria Stevens - Turn-of-the-century Stanford alumna paved path for women in biology" (PDF). Stanford Historical Society. Archived (PDF) from the original on July 5, 2010. Retrieved August 18, 2013.
  6. 1 2 Gilgenkrantz, Simone (October 15, 2008). "Nettie Maria Stevens (1861-1912)" (in French). Clérey-sur-Brénon, France: Médecine/Sciences. Archived from the original on August 17, 2013. Retrieved August 18, 2013.
  7. 1 2 3 "MSU Authentication | Michigan State University". doi:10.1093/acref/97801996%20666.001.0001/acref-9780199766666-e-465.
  8. ↑ Morgan, T.H. (October 12, 1912). "The Scientific Work of Miss N. M. Stevens". Science 36 (298): 468–470. doi:10.1126/science.36.928.468. JSTOR 1636618.
  9. ↑ Wessel, Gary M. (September 13, 2011). "Y does it work this way?" (PDF). Molecular Reproduction and Development (Wiley) 78 (9). doi:10.1002/mrd.21390. Retrieved August 20, 2013.

Further reading

External links

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