Luigi Luca Cavalli-Sforza (1922-2018)

Luca (as many o f us called him), went to medical school in Pavia (Italy) and graduated in 1944. He disliked medical practice. He joined the group o f Sir Ronald A. Fisher in Cambridge in 1949, as an Assistant in Research. In Cambridge, he worked on the genetics o f E. coli, which at the time was a new field. He isolated a mutant strain o f E. coli that he and others would later use to discover and clarify the nature o f ‘bacterial sex’ (conjugation). While in Cambridge, he had established collaboration with Joshua and Esther Lederberg. Over the next eight years, Luca and the Lederbergs published definitive results on conjugation. He returned to Italy in 1950 initially to a Milan pharmaceutical company and soon after joined the University o f Parma. The topography o f the region around Parma was mountainous. The villages in the mountain valleys were small and isolated. In these villages, people mostly married their relatives within the villages. The villages in the plains were relatively larger and connected. Outbreeding was common in these villages. R. A. Fisher had theoretically worked out that the main consequence o f small size o f a population was that variation in the frequency o f a gene variant will fluctuate unpredictably from one generation to another; a phenomenon not observed in large populations. Luca empirically demonstrated that this was true through his systematic studies on blood group frequencies in the villages o f the mountain valleys and plains o f Parma. He made a name for himself as a teacher and a geneticist. He joined (I have heard that he was invited to join) Stanford University in 1970 as a Professor and worked there until 1992.