While a graduate student at the University of California, Los Angeles, Raven and Harlan Lewis published a major paper in 1958 on the evolution of "C. franciscana", and generalized to what was by then a general a pattern of speciation in "Clarkia". They concluded that "C. franciscana" had evolved from "Clarkia rubicunda"; and they asserted that "C. franciscana's" origin mirrored a recurring theme in "Clarkia" of a derived species showing a close morphological similarity to a parental species, the derived species being geographically proximal, but differing from the parent by chromosomal differences and showing interspecific sterility. Further, they hypothesized that such speciation in "Clarkia" was rapid, and perhaps occurred within the last 12,000 years.