In 2015, Ohta and Richard Lewontin were jointly awarded the Crafoord Prize "for their pioneering analyses and fundamental contributions to the understanding of genetic polymorphism".

Having failed the examination for medical school, she transferred to the agriculture department at Tokyo University and majored in horticulture.

[4] Hitoshi Kihara gave Ohta an opportunity to study abroad,[6] and in 1962, she entered the graduate program at North Carolina State University with support from a Fulbright scholarship.

She worked with her advisor, Ken-Ichi Kojima, on problems in stochastic population genetics,[6] Ohta completed her PhD in 1966.

However, in 1966, Richard Lewontin and John Lee Hubby found a much greater than expected amount of genetic variation among the individuals in a population.

[15] Ohta's theory of slightly deleterious fixations introduced a new class of origin-fixation models, with the goal of better explaining observed data.

)[10] As a result, mutations that are slightly deleterious can become more easily fixed in small than in large populations, through genetic drift.

[10] When Ohta first published her Nearly Neutral theory, she faced difficulty in attracting the scientific research community's attention and acceptance.