I just found out that Walter Fitch died last week. Here's the link to the announcement posted on Panda's Thumb. On that page, read not only the announcement but the second comment from Joe Felsenstein reflecting on Fitch's influence.
Fitch was definitely a pioneer in molecular evolution. In addition to the contributions that Felsenstein noted, he's also the author of one of the most significant conceptual arguments for the common ancestry of proteins (which has 765 citations according to Google Scholar):
Fitch. 1970. Distinguishing homologous from analogous proteins. Syst Zool 19:99-113.
Part of his argument depended on the tree-like branching pattern you could obtain from protein sequences, and part of the argument rested on correspondence of the protein-derived phylogenetic tree with the fossil record. It's still a compelling argument that creationists would be wise to study very carefully.
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