Discours de remerciement – Berne, 16.11.1999 (anglais)

Italie/États-Unis

Luigi Luca Cavalli-Sforza

Prix Balzan 1999 pour la science des origines de l'homme

Pour l'ampleur de ses travaux sur l'évolution de l'homme, qu'il a menés en étudiant à la fois les aspects génétiques et culturels.

Mrs. President of the Swiss Confederation,
Members of the Balzan Foundation,
Ladies and Gentlemen,

I would like to begin by thanking all my friends, and other people I do not know, for proposing my name for the Balzan Prize; the Prize Committee, for their decision to act on the nomination; and above all, Eugenio Balzan and his daughter Angela Lina Balzan for their great generosity to science and culture. – For about the last thirty years I have been living in the United States where I frequently have cause to admire the large-scale sponsorship that exists there – particularly in the scientific field – and from which universities and cultural institutions benefit to a substantial extent. And I often think what a pity it is that there is so little sponsorship in Italy. One of the reasons, of course, is that Italian legislation does not particularly encourage generosity of this type, except in special cases, and then only recently. For this reason, the way of thinking that would encourage very wealthy people in Italy to donate part of their money to the country’s scientific, cultural and intellectual progress has never been able to establish itself there. However, I hope that the generosity of the Balzans will stimulate more people in Italy to act in a similar manner. Based on what I know of the life and work of Eugenio Balzan and his daughter I feel enormous admiration for them, and I am sure their memory will be held in great respect by the many others who have benefited from their generosity in the same way as I have. I would like, once again, to express my deepest gratitude to those who decided to make the award to myself and my field of learning. 

The Balzan Prize has been awarded to me for my research into the origins of man. The first ten years of my work as a researcher were devoted to the genetics of bacteria. However, in 1952, in Italy, I remembered the original teachings of my great mentor in the field of genetics, Professor Adriano Buzzati-Traverso. I owe to him my interest in the genetics of population and evolution, and I decided to turn to this interest, and to concentrate it on humans. I feel the choice of humans was dictated by my university studies, which I completed in medicine. 

The study of evolution received a solid framework with the introduction of a mathematical theory which was developed between 1918 and 1950 by three great scientists, Sir Ronald A. Fisher, J. B. S. Haldane and Sewall Wright. From 1948 to 1950 I had the good fortune to work with Sir Ronald Fisher in Cambridge and derived great benefit from the relationship. Soon after this, I found myself asking the question as to whether it would be possible to reconstruct the evolutionary history of man by analysing the genetic differences between humans living today. At that time there were not yet sufficient genetic population data. Knowledge was limited to the frequency distributions of certain blood groups, including the so-called ABO system used for blood transfusions, and the famous rhesus system, as well as a few others. So until enough additional scientific knowledge could be collected to form a critical mass, the time could be devoted to studying the theory of evolution. At that time, there were two fundamentally different views as to the significance of the two major evolutionary factors: natural selection, on the one hand, and on the other, the effects of chance due the limited size of populations. This inevitably leads to fluctuations in the statistical frequency of occurrence of genetic characteristics, and their effects would accumulate over generations. 

There was absolutely no doubt that natural selection played a central role. The influence of chance had already been especially investigated by one of the fathers of the mathematical theory of evolution, Sewall Wright, but there were still no usable empirical data. In passing, I am pleased to be able to remind you that Sewall Wright was awarded the Balzan Prize in 1984, having outlived the other two by a good many years. The other geneticist who so far had the honour of receiving this prize was John Maynard Smith, who was one of the most brilliant students of J. B. S. Haldane. So we have the interesting coincidence that of the three geneticists who have been awarded the Balzan Prize until now, Sewall Wright was the last of the three great names who was still alive, and the other two were students of Haldane and Fisher.

I set out to solve the problem of how to measure the effects of chance on genetic variation by studying a population group in the neighbourhood of the University of Parma where I was teaching in the nineteen-fifties. The idea was that it should be easy to predict the effects of chance on the genetic differences between the various villages, by using demographic data reconstructed on the basis of church records of births, marriages and deaths going back to the year 1500. This would permit us to calculate the genetic variation due to chance predicted theoretically, and compare it with actual observations. This work turned out successfully thanks to the assistance of two young students: the priest Antonio Moroni, and Franco Conterio, who are both now professors at Parma, the former of ecology and the latter of anthropology. 

By 1961 enough genetic data and observations from numerous populations in the world had been collected, and it was possible to make a first analysis of the evolutionary tree of human populations. Anthony Edwards of Cambridge University helped me to develop and use methods of reconstructing evolutionary trees. We performed the necessary heavy calculations with the Olivetti Elea computer recently purchased by the University of Pavia, to which I had moved and where I was continuing my research work. We could thus reconstruct the first evolutionary tree of human populations, whose basic structure is still valid today. Another working relationship very fruitful for me was with Sir Walter Bodmer, also a student of R. A. Fisher, with whom we published two books on human population genetics. One of these, The Genetics of Human Populations, was re-printed only a few months ago by Dover Publications, almost thirty years after it was first published.

In the second half of the nineteen-sixties I extended the model of genetic research I had developed on the population of Parma – as far as this was possible – to a group of hunters and gatherers in the African bush: the pygmies. This is one of the few population groups still alive today with a pre-agricultural economy similar to that of the Palaeolithic period. Professor Marcello Siniscalco, at that time Professor at Leiden, was very helpful to me in carrying out in his laboratory the genetic analysis of countless blood samples I had collected in Africa. The contact with such a totally different culture stimulated me to embark on research into cultural evolution which I pursued after I moved to Stanford University in 1971. I began by analysing archaeological data on the spread of agriculture in Europe in the Neolithic period in collaboration with the archaeologist Albert Ammerman. Thanks to a mathematical theory developed by R. A. Fisher in 1937 we were able to measure the rate at which agriculture spread, and show that it was consistent with the hypothesis that it was the people themselves that spread, and not the knowledge of agriculture. In other words, it was a diffusion of farmers, which we called demic, and not of farming. In the second half of the nineteen-seventies we carried out with Alberto Piazza and Paolo Menozzi, now Professors of Human Genetics in Turin, and Ecology in Parma, an analysis of data on gene frequencies in Europe. This work enabled us to confirm that genetic and archaeological data are closely correlated and consistent with the idea that agriculture spread from the Middle East. This was the start of a 14-year-long working relationship with Menozzi and Piazza. Thanks to it we extended these studies of genetic geography and history to the rest of the world, in the way they are described in the book The History and Geography of Human Genes published in 1994.

In the nineteen-eighties the first methods of genetic analysis were used which made it possible to carry out direct investigations on DNA. This revolutionary development expanded the bandwidth of genetic variation from a few hundred genes to several tens of thousands, and genetic analysis could be shifted down to the smallest unit of DNA, the individual nucleotide. It also became possible to use new methods of collecting genetic data on significant factors in human evolutionary history, particularly on the spread of modern man beyond the area from which he originates: Africa. Four years ago, a researcher from my laboratory, Peter Underhill, together with Peter Oefner, a colleague from Ron Davis’ laboratory, invented a new and particularly efficient method of investigating DNA differences. This made it possible to find many genetic variations in the Y-chromosome. For a number of reasons this chromosome turned out to be extremely valuable, even though it had made practically no contribution to evolutionary research up to that time. Since then, however, we have entered a phase of great activity and fascinating discoveries.

The explosive growth in knowledge in the last few years has also had an effect on certain socio-cultural fields of study such as linguistics and onomastics – the study of names. In connection with my studies of onomastics and blood relationships I would like to acknowledge the valuable support of Professor Gianna Zei of Pavia. We have observed a significant similarity between the development of language and of genes, which is in part due to common evolutionary mechanisms and historical expansionary processes of populations. With the studies of the development of language I have had the assistance of Joseph Greenberg and Merritt Ruhlen of Stanford, and Bill Wang of Berkeley. These latest studies result in part from thirty years of collaboration with Professor Marc Feldman of Stanford, with whom we developed a mathematical theory of cultural heredity. Until now the studies of cultural evolution have not aroused much interest among cultural anthropologists, with one important exception: the joint research on the pygmies with Professor Barry Hewlett of Washington University. The studies have, however, proved interesting to economists who find the mathematical approach more appealing.

My research work has frequently led me into areas normally out of bounds to the natural sciences, and it can therefore promote a greater interchange between the « Two Cultures ». Multidisciplinarity is central to fields such as mine. On the other hand, science demands ever-increasing specialisation, because otherwise there is the danger of superficiality. However, it is always possible to become multidisciplinary by seeking out good co-workers in other disciplines. I am pleased I have had the opportunity to mention the most important ones and to thank them. My research work would not have been possible without them.