Russell F. Doolittle (January 10, 1931 – October 11, 2019) was an American biochemist who taught at the University of California, San Diego (UCSD). Described as a "world-renowned evolutionary biologist",[1] Doolittle's research primarily focused on the structure and evolution of proteins.[2] Highlights of Doolittle's decades of research include his role in co-developing the hydropathy index and determining the structure of fibrinogen.