On January 3rd, James F Crow died, at the ripe old age of 95. Jim was one of the 20th century's most prominent population geneticists, training many other leaders in the field as well as providing much of the evolutionary theory we have today. Madison, Wisconsin must be a healthy place to live because, among other things, Jim's predecessor and one of the ultimate founders of population genetics, Sewall Wright, lived and passed away there. Wright lived til he was just shy of his 100th birthday, so perhaps Madison is just too tough a place to make it all the way.
I knew Jim from several meetings, though not as a close friend. But all of us in our generation were weaned on Crow and Kimura (the latter, a founder of the 'neutral' theory of evolution as a counterweight to the prevailing strongly selectionist view, was a Crow student). Many other of our most prominent population geneticists trained or worked with him. His Wiki page stresses his role in teaching, suggesting it may have been his most important single contribution. If one includes his books, and his very clear arguments about various subjects in his papers, then it would be hard to argue with that.
Crow may not be known for many specific major theorems or the like, but he worked extensively on the nature of natural selection and how to detect evidence of it, on the way interactions among genes were (or, he might insist) were not reflected in adaptive evolution, on the age effect of fathers on disease risk in their children, and on human population variation--these being things I knew him for (he also did experimental and fruit-fly work).
Jim Crow was personally a gentle man and a gentleman. He was well-rounded personally and in his family. I cribbed the picture, showing him playing the viola as he did for the Madison Symphony, from John Hawkes' very fine post, where you can learn more about Crow (John is at Wisconsin).
As I personally witnessed, he could defend a point of view in discussions, but I never knew him to become aggressive about it, nor ad hominem, even when his protagonist was a bully (something I myself witnessed, the bully being alpha male Jim Neel). He stuck to polite consideration of issues--even though he did have his points of views!
Like the other famous Jim (Watson), Crow did hold some views about human variation, that (I think) in naive ways conflated the facts that we're all genetically different, that genes affect our traits, with group (i.e., 'race') differences. But we all have our blinders.
In his later, retired years, Jim continued to contribute and one noteworthy way was his editing of a column of retrospectives that ran in each issue of the prominent journal Genetics. These looked back at major issues and historical figures in ways that might not be widely known among younger readers for whom history was not considered a very important part of science.
Jim had nowhere near the name-recognition of the great triumvirate of population genetics, Wright, JBS Haldane, and RA Fisher. In recent years, I've found that people in genetics often have not heard of him (to their knowledge). But even the great troika, along with other giants in science of their time, are no longer remembered by name. And Jim had the kind of career, and of kindness, that should satisfy anyone in or out of science.