Hrdy changed course in mid-year and entered Harvard as a graduate student in 1970 to study primate behavior. She focused her PhD research around a field study of Hanuman langurs. On the advice of Professor S.M. Mohnot, it was carried out in the area of Mount Abu, India. Her thesis advisor was Irven DeVore. She also worked closely with members of her thesis committee such as the evolutionary biologist Robert L. Trivers and E. O. Wilson. She received her thesis from Harvard in 1975.