Matilda effect
Nettie Stevens (1861–1912) – Discoverer of how chromosomes make living things male and female.   Her studies of mealworms showed for the first time that a living thing's sex is caused by its chromosomes and not by its environment. Stevens greatly influenced the scientific community's transition to this new idea: chromosomal sex determination. However, Thomas Hunt Morgan, a distinguished geneticist at the time, is generally credited with this discovery. Even though she did a great deal of work in genetics, Stevens' contributions to Morgan's work are often disregarded.