Luigi Luca Cavalli-Sforza (1922-2018).

Luigi Luca Cavalli-Sforza passed away on 31 August 2018. Born in Genoa, Italy, in 1922, at age 16 he began his undergraduate studies in medicine in Torino and continued them the next year in Pavia. At age 20 he began publishing research papers on quantitative measurements of bacterial virulence. In this fijield he worked with his classmate Giovanni Magni, performing experiments using mice inoculated with virulent bacteria. They discovered a linear relationship between mean death time and the logarithm of dose (i.e., the number of bacteria used for inoculations) and proposed an interpretation that isolated the two factors of virulence: the reproduction time of the bacteria and their toxicity (which are related, respectively, to the slope and the intercept of the linear relationship) (Cavalli and Magni 1947). In 1944, Cavalli-Sforza fijinished his undergraduate studies and had already published eleven research papers. These were followed by six papers the following year, including his fijirst one coauthored with Adriano Buzzati-Traverso (BuzzatiTraverso and Cavalli 1945), who was his teacher in a genetics course in 1942. Cavalli-Sforza had met Buzzati-Traverso after three years of looking for a mentor who could teach him how to become a researcher (Cavalli-Sforza and Cavalli-Sforza 2005). Buzzati-Traverso’s complete dedication to science deeply impressed Cavalli-Sforza, who considered him one of the people who had a major influence on his life. Their fijirst joint research papers dealt with population genetics of Drosophila (BuzzatiTraverso and Cavalli 1945) and planktonic organisms in lakes (Baldi et al. 1945). At the end of World War II no jobs were offfered at Italian universities, and Cavalli-Sforza worked as a doctor in a hospital during 1944–1945. Discouraged by the lack of drugs to help patients, he found a job at the Istituto Sieroterapico Milanese, a pharmaceutical institute in Milan (Cavalli-Sforza and Cavalli-Sforza 2005). There, during the mornings he extracted blood from patients and did other works, and in the afternoons he managed to perform research experiments that led to publications on quantitative analyses of bacterial resistance to X-rays and other mutagens (Buzzati-Traverso et al. FIGURE 1. Luigi Luca Cavalli-