Genetics pioneer who insisted the idea of race was unfounded
Luca Cavalli-Sforza obituary: Collaborator with great Irish geneticist William Hayes
Born: January 25th, 1922
Died: August 31st, 2018
The geneticist Luca Cavalli-Sforza has died aged 96. A pioneer of human population genetics and member of the Royal Irish Academy, he is best known for reconstructing the history of human populations through studies of genetic variation. He is regarded as the father of the field of genetic anthropology. By illustrating the biological continuity between populations and nuances resulting from continual migration both within and across political borders, Cavalli-Sforza insisted that the idea of race was unfounded and serves no purpose.
Luigi Luca Cavalli was born in Genoa on January 25th, 1922, the only child of Pio Cavalli and Attilia (Manacorda) Cavalli. His father represented US companies that sold washing machines and dishwashers in Europe; he also wrote a book on advertising, La Spada dell’America (America’s Sword), published in 1919.
Luigi Cavalli added Sforza to his surname as an adult after his father had died, taking it from his maternal step-grandfather, who had adopted him. He earned a medical degree from the University of Pavia in 1944. Studying medicine during the second World War might have saved his life, he later told colleagues: Italy did not draft medical students.
Cavalli-Sforza worked as a physician in Italy for two years. Medicine then was not advanced, antibiotics were unavailable and the work “was really more a job for a priest”, he told Feldman in a videotaped interview in 2006.
“You couldn’t help anybody,” he said. “You just saw people dying, and you couldn’t do anything to help them.”
The experience prompted him to move away from clinical medicine towards microbiology and then genetics.
In 1946 he married Alba Ramazzotti, a niece of one of his professors. She had studied biology but did not pursue a career in it. He moved to Cambridge, and worked as an assistant to Ronald Fisher, professor of genetics, one of the architects of evolutionary mathematical theory, and among the finest statisticians of the 20th century. Under Fisher’s direction he conducted experiments on genetic recombination in bacteria, building on the research of Joshua Lederberg.
This led to connections with the great Irish geneticist William Hayes, who proposed that genes were transferred between bacteria in a unidirectional fashion (from a donor to a recipient) during the process of conjugation. Breakthroughs in bacterial genetics contributed importantly to the modern understanding of genetics and the technology of genetic engineering as well as the spread of antibiotic resistance in bacteria.
Shift in focus
Cavalli-Sforza’s focus shifted from bacterial to human genetics, which, post-war, was a minor field. He began lecturing in genetics and statistics, first at the University of Pavia and later in Parma. During this period he initiated a ground-breaking piece of research, reconstructing the genealogies of 70 villages distributed along the Parma valley. Combining genetic data collected from the villagers with 400 years of genealogical records from the parish archives, he analysed the data using the statistical techniques learned from his time with Fisher. The results were remarkable – he illustrated the importance of the random transmission of heritable traits, despite the forces of natural selection, which had previously been considered the principal driver of evolution. This observation would in later years be confirmed and extended to all of molecular evolution, via the work of the Japanese geneticist Motoo Kimura.
In the early 1960s, genetic data on human populations increased from blood group typing and the study of protein diversity. Cavalli-Sforza pioneered the application of statistical modelling to these data, leading to a reconstruction of human evolution and population history. In collaboration with another student of Fisher, Anthony Edwards, he created the first genealogical tree of humanity. With Walter Bodmer (who also studied with Fisher), he published The Genetics of Human Populations, the first comprehensive scholarly work in the field of human population genetics, which took into account the newly acquired knowledge of genetic polymorphisms in humans. He quickly recognised the importance of African populations in the genetic story of humanity, and over the following 30 years conducted eight research expeditions to the African rainforests, to study the Pygmies, one of the oldest human populations, who allowed him to collect genetic and anthropological data for his work. During this period he developed a vast collaborative global research network for the study of human genetic variation.
In 1971 he took up a professorship at Stanford University. The increasing resolution and steady flow of genetic data from human populations allowed Cavalli-Sforza and his collaborators to reconstruct, with ever greater precision, the biological evolution of humanity. He connected findings from his genetic work to the study of cultural evolution. In collaboration with archaeologist Albert Ammermann, he studied the spread of agriculture across Europe, demonstrating it was largely due to the spread of people, rather than the diffusion of technology. In 1997, together with Alberto Piazza and Paolo Menozzi, he published the seminal The History and Geography of Human Genes, a collection of more than 800 graphs that provided the first global view of human genetic variation. With linguists Joseph Greenberg, Merritt Ruhlen and Bill Wang he suggested that human languages had evolved and diversified in parallel with human genes.
Throughout the 1990s, Cavalli-Sforza collaborated in establishing the Human Genome Diversity Project, a collection of genetic data from representative global populations made available to geneticists to learn more about the history of the human species. In the early years of the new millennium he and his Stanford team, taking advantage of developments in DNA sequencing technology and resources provided by the project, reconstructed the genealogical tree of the human Y chromosome (which determines the male sex and is passed from father to son), back to the common ancestor of all males (sometimes referred to as “Adam-Y”), whose Y chromosome, in different forms, all males carry.
His last project, published almost 10 years ago, shows the slight, but continuous, loss of genetic diversity from east Africa (the origin of human movements out of Africa), to the Pacific Islands (the farthest point of human dispersal). It is a result that fully confirms both our African origin and the importance of chance in evolution, but above all illustrates the ways in which human diffusion took place on the planet, through a series of stages marked by “founder effects”. His legacy will affect the study of genetics for generations to come.
Cavalli-Sforza died peacefully on Friday, August 31st, in the presence of his family, at his home in Belluno, Italy. He is survived by his four children, Matteo, Francesco, Tomasso and Violetta