There is a social media debate about whether Dr. Tomoko Ohta should get the credit as the initiator and primary contributor of the Nearly Neutral Theory. In my mind, her name has always been synonymous to the Nearly Neutral Theory, so I was puzzled and wanted to figure out if I was wrong.
Since this is an important chapter in the history of population genetics, and because young scientists are often curious about what is it like to be a giant and to have worked with other giants, I decided to ask Dr. Ohta if she could clarify her contribution and comment on some other related issues. Luckily, my e-mail found her, and she replied.
Her narratives, help clarify the history to scientists who care about who and when, in addition to how and why, and shed light on how ideas and research evolve.
Here are a few things I have learned from my correspondence with Dr. Ohta. (With the permission from Dr. Ohta, I am sharing this exchange).
Regarding the history before the Nearly Neutral Theory.
“The idea of importance of slightly deleterious mutations goes back to H J Muller, Our load of mutations, 1950. The point is that it was based on phenotypes. So were the arguments of Kimura, Crow, Maruyama and others in 1960s. Also someone says that Darwin recognized existence of neutral variations. All these discussions were based on phenotypes.”
Regarding Kimura’s Neutral Theory and her own role in the Nearly Neutral Theory.
“Kimura’s neutral theory is concerned with the evolutionary changes at the molecular level. So is the nearly neutral theory. Now, my contribution is mainly on the behavior of nearly neutral mutant genes in populations, and on how it differs from the strictly neutral case. The prediction of the neutral theory on evolutionary rate and polymorphisms is simple and nice as everyone knows. Kimura liked the simple and elegant theory and did not like complicated problems. Once slightly deleterious (weakly selected) mutations are incorporated into account, the problem becomes very complicated. I thought that natural selection is not so simple as Kimura says, and presented the nearly neutral theory. Here interaction of selection and drift becomes very significant.”
Regarding Kimura’s work on Nearly Neutral Theory:
“Kimura recognized the significance of the nearly neutral theory in 1970’s, and published a couple of papers on this.But his discussion had been mostly on the strictly neutral mutations afterward.“
Regarding Neutral vs Nearly Neutral and their hot discussions:
“I and Kimura, sometimes including Crow, have had many hot discussions on the problem. I had often been criticized.”
Regarding how to move the field forward:
“Rather than going back to the credit problem, people should study about the recent progress on molecular processes of gene expression, that is very interesting. Numerous molecular interaction systems are working together at the chromatin level, for controlling gene expression patterns in various tissues and organs. It is remarkable that such complex systems evolved. I would like to say that the nearly neutral processes have been quite important for their evolution. Molecular machineries are connected directly or indirectly forming large network systems. We may need to investigate evolution at the systems level in the future.”
Regarding the work environment as a female scientist in Japan
In addition to these, Dr. Ohta mentioned that she did not have much gender problems in her research career, she has been able to discuss freely with people in Japan, and she thinks the research environment is good. She also mentioned that Kimura had been nice on this.
After seeing what I have written, Dr. Ohta corrected me that she is not a giant, but she probably has been lucky that she could do her work at the best time in the beginning of molecular evolution. I have to respectfully disagree with her about the first part-- she has been a giant, she has worked side by side with another giant, she has worked on the shoulders of previous giants, and on her shoulder future giants will stand.
She also said: “I am very glad to know that the comments are useful for young people like you. From the time of Darwin, evolutionary biology is related to many different fields of biology, and nowadays many areas are developing so rapidly. So it is a difficult but interesting time for us.”
I very much appreciate Dr. Ohta taking the time to clarify the history to a random unknown trainee. Quoting a story that perhaps explains this "When I was young, I sent my letter and paper on slightly deleterious mutations to S Wright. He sent me back the letter saying how his shifting balance theory was different from mine, but his theory also might explain the data. I was happy to receive the letter, as some younger seniors did not respond to me. So I responded to you."
July 6th, 2019