[5] According to Nicole Hahn Rafter, she was there for five years doing graduate work in zoology and wrote her book The Primitive Streak and Notochordal Canal in Chelonia (1896).
She also did research on embryology using turtles, studied the differences between Sargatia (a type of sea anemone) and starfish as well the variations on other organisms.
For example, her interests in the early 1900s included the "Tribe of Ishmael," an ethnic group frequently studied by American eugenicists, and the heredity exhibited in children of interracial marriages, suggesting that Gertrude may have played a considerable role in influencing Charles' interest in eugenics and his subsequent career development.
Using the work of Dr. Jörger from a Swiss insane asylum, Davenport discusses the favorable or "good" branches of the Zero family, characterized by industriousness, fiscal responsibility, good manners, strong morals, and in-group marriage, in comparison to the unfavorable branch, characterized by criminal behavior, alcoholism, vagabondage, and marriage to foreign women.
Davenport remarks upon hereditary explanations for the two branches; she examined their physical phenotypes and even attempted to exclude environmental effects by considering the vagabondage developed in Zero children taken from their families and distributed to respectable caretakers.
Her piece pushes a strong attitude associating degenerate heredity with matrilineal inheritance, as she traced the lineage of the criminal branches of the Zeros through blood-related and insane women.
Davenport did not advocate for negative eugenics at the time, believing that the decline heredity and physical phenotypes of the vagabond branch would bring about its extinction on its own.
She believed these misguided efforts to be a result of excessive comfort with civilization and forgetfulness of the natural selection that produced humans who attained it.
Gertrude described how a growing population of those "incompetent thru such bad heredity as imbecility, criminality, and disease entail" costing taxpayers significant and increasing losses, and described the developing eugenics movement under Francis Galton, Leonard Darwin, and her husband at Cold Springs Harbor as the solution.
[23] During the course of these studies and publications, the Davenports explored how human traits, specifically skin pigmentation, eye color, and hair characteristics, were passed on to the next generation with Mendelian genetics.
[21][22][23] Gertrude also individually authored the monographs The Primitive Streak and Notochordal Canal in Chelonia (1896)[24] and Variation in the Number of Stripes on the Sea-anemone, Sagartia luciae (1902).