1cavalli_sforza_luigi_luca_genes_peoples_and_languages
.pdfAcknowledgments
This book owes much to many people. It was conceived when I was invited in 1981 and 1989 to give a series of lectures at the College de Fril1lce. The "College" is a wonderful institution created by Francis I to counteract the arrogance and backwardness of the Sorbonne, and to exemplify a center of excellence. Jacques Ruffle's arrangements motivated me to write my lectures, and gave me the wonderful chance to twice spend a month in Paris in the spring, delivering them. In 1994, Odile Jacob expressed interest in publishing the lectures in a new series of books based on courses at the College, and so I rewrote my lectures from scratch for the third time. The Italian edition was a fourth opportunity. My former student Mark Seielstad was not deterred by significant differences between the French and the Italian editions, but used them both in order to improve the English translation, which he completed while in the throes of preparing his Ph.D. dissertation at Harvard. The need to revise the English edition was also a new and irresistible temptation for me to update and modify the book again. This fifth
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version has been edited with great skill and attention to clarity, rigor, and accuracy by Ethan Nosowsky. I am also grateful to Phyllis Mayberg for her help in preparing the manuscript and to Brian Blanchfield for ushering ino press.
Collaboration with experts from other fields is essential when taking a multidisCiplinary approach. I am indebted to many friends and colleagues who, over the last fifty years, have helped lay the foundation for the scientific work described in this book. As an expression of gratitude, I'd like to summarize the major collaborations of these many decades.
I began as a geneticist researching bacteria in the forties. In the fifties, when I was teaching part-time in the University of Parma, Italy, I gradually shifted focus to human population genetics. My main research at Parma was the study ofthe role ofchance in evolution, a subject that was neglected at the time. The opportunity to give a clear, quantitative answer to the problem was offered by the demographic records of the last three centuries or more in a region where the population density varied enormously, very high in the fertile plains, very low in the mountains. Sizes ofvillages and migration among them could be estimated from the available parish books. When there are few parents to pass genes from one generation to the next, chance will cause important fluctuations in the frequencies of types of genes found in different villages. The effect of chance in evolution is called "drift; a somewhat misleading name, because the word practically has the opposite meaning in other sciences. This research made it possible to predict the variation between villages due to drift on the basis of their demography, and compare it with local genetic variation. This work and a parallel study of consanguinity data from bishopric archives would not have been possible without the advice, information, and help of Antonio Moroni, a Catholic priest, then my student and now professor of ecology at Parma, and Franco Conterio, then postdoctoral fellow and now professor of Anthropology at Parma.
In the sixties I moved to the University of Pavia, Italy, and started generating methods for reconstructing evolutionary trees of human genetic data, in collaboration with Anthony Edwards, now at Gonville
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and Caius College of Cambridge. Afterward I researched African Pygmies in many expeditions between 1976 and 1985. This work profited greatly from my collaboration with Marcello Siniscalco. then professor at Leyden. as well as witll anthropologists Colin Turnbull, now. unfortunately, deceased. and Barry Hewlett, now a professor in Vancouver, Washington. Our work was the subject of a book I edited, published in 1986. called African Pygmies.
It soon became clear that human population genetics research, touching as it does on many disciplines, could prosper only with the help of scientists from othe~ disciplines. I moved to Stanford in 1971 and collaborated with archeologist Albert Ammerman, now at Colgate University, on the problem of whether, in the expansion of Neolithic agriculture from the Middle East to Europe. the farming technique or the farmers themselves diffused northwest from the place of origin. The study of genetic geography was begun in 1977 with the collaboration of Paolo Menozzi and Albelto Piazza, now professors of ecology at Parma and. of human genetics at Turin respectively. with the purpose of offering a solution to that problem, and we provided a key to the answer. Eventually this approach was extended to the rest of the world and led to the publication of our History and Geography of Human Genes in 1994 with Princeton University Press. It is the source for the majority iJfclaims made in the first five chapters of this book. and is referred to by the acronym HGHG.
In the seventies and early eighties I dedicated much time to the study of cultural evolution, mostly as a response to the personal and profound interest I developed after observing African Pygmies. Researching cultural transmission and evolution, I gainfully collaborated with Marcus Feldman, professor of biology at Stanford. Applications to linguistic evolution were made possible thanks to exchanges with linguists from the Bay Area: Bill Wang, from Berkeley, Joseph Greenberg and Merritt Ruhlen at Stanford.
At the end of the seventies and beginning of the eighties, with the seminal work ofY. W. Kan; David Botstein, Ronald Davis, Mark Skolnick, and Ray White, the promise of chemical analysis of DNA-:-the material of heredity-started to become reality. Until
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that time, genes-the units of inheritance-were interpreted only through their products, mostly proteins. From then on it became possible, and eventually much easier, to study variation on DNA directly. .
Mitochondrial DNA, a small organ that is present in every cell and transmitted to the progeny by the mother, was one of the first objects of study. We began this work with Doug Wallace and his students. In the hands of the late Allan WIlson of Berkeley, it gave the first important· evidence that modem humans appeared in Africa and from there spread to the rest .of the world. Now the purposes of our research are also served by studying Y chromosomes, found only in males and transmitted from father to son. I was blessed by a stroke ofgood luck when Peter Underhill ofmy laboratory and Peter Oefner of Ron Davis's laboratory together developed a superior technique of detecting DNA variation. 111e new genealogy of Y chromosome variants they developed will enormously aid our understanding of the history of the evolution of modem humans. This research is now progressing rapiclly.
The results already at hand promise to generate a clear picture of
the expansions and migrations out of Africa tllat made modem humans look the way ti~eydo today. It would seem that these events
were mucl1 more recent than has b~en thought. It is impossible to generate much diversity in such a short period of time, which convinces us once and for all that the superlicial racial differences we perceive between people from different continents are just that.
XII
GeDe.s, Pe0pIe san d l anguage s
CHAPTER I
Genes and History
The Pride of an Emperor
Dante Alighieri's reputation as the grand master of Italian literature has eclipsed all the Italian poets and writers who followed him. Nevertheless, Dante was not the only great Italian poet. There were others, such as Petrarch, Ariosto, and Leopardi. The latter is perhaps the least well-known outside Italy, although he was not only a talented poet but also a remarkable philosopher.
I recently reread his play Copernicus, which I still find relevant and insightful. The characters include the Sun, the First and Last Hours ofthe Day; and Copernicus. In the opening scene, the Sun confides to the First Hour that he is tired of revolving around the Earth each day, and demands that the Earth shoulder some of the burden. The First Hour, alarmed by this prospect, pOints out that the Sun's retirement would create havoc. But the Sun is adamant and insists on informing Earth's philosophers of the impending change since he believes they can convince humans of anytlling--good or bad. By the second scene, the Sun has delivered on his threat. Copernicus,
sUlprised by the Sun's failure to rise, sets about investigating the cause. His search quickly ends when he and the Last Hour are summoned to hear the Sun's proposal: the Earth must renounce her position at the center of the Universe'and instead revolve around the SUllo Copernicus notes that even philosophers would have difficulty convincing 'the Earth of that, Moreover, the Earth and her inhahitants have grown accustomed to their position at the center of the Universe and have developed the "pride of an emperor." A change of such magni- n,;de would have not only physical but also social and philosophical consequences. The most basic assumptions about human life would be overtumed. But the Sun is insistent that life will go on, that all the barons, dukes, and emperors will continue to believe in their importance, and that their power won't be weakened in the least, Copernicus offers further objections: a galactic revolution could begin-the other planets may assert that they want the same rights to centrality as the Earth had, Even the stars would protest, In the end, the SUll might lose all impOltance and be forced to find another orbit. But the Sun desires only rest and counters Copen1icus's final fear-that he will be bumed as a heretic-by telling him he can avoid such a fate by dedicating his book to the Pope.
In Wliting about Copernicus, Leopardi had the benefit ofliving several centuries after him, He knew what had happened to Copernicus, Giordano Bruno, and Galileo. But we do not have Leopardi's advantage when considering the Scientific issues of our day. Any current theOlies may be modified or even destroyed at any moment. In fact, science progresses because every hypothesis can be confirmed or rejected by others. The great number of conditionals we use in our scientific prose underscore this truth. While correcting the translation of one of my books, I was terrified to see that all my conditionals had been changed to indicatives-my safeguards had been eliminated. When we write papers for scientific journals, we know that many statements cannot be supported in their entirety. This seems strange to the public: isn't science infallible? In the end, only religion claims to deliver certainty. In other words, faith alone is immune from doubt, although few believers seem troubled by the fact that each religion offers different answers. Mathematics
may be the only exception in the sciences that leaves no room for skepticism. But, if mathematical results are exact as no empirical law could ever be, philosophers have discovered they are not absolutely novel-instead., they are tautological.
Copernicus also reminded me of our attitudes about race and racism. Each population believes that it is the best in the world. With few exceptions, people love the microcosm into which they are born and don't want to leave it. For Whites, the greatest civilization is European; the best race is White (French in France and English in England). But what do the Chinese think? And the Japanese? Wouldn't most of today's recent immigrants return to their country ifthey could find a decent way of life there?
It is also true, as Leopardi observed, that the more things change, the more they stay the same. Noble or economically powerful families come and go-there is an increasingly rapid turnover ofpowerbut power structures change very little. The Roman Empire lasted longer than many others in Europe, but it spanned only five centuries. It was similar in size to the Inca Empire, which lasted a little more than a century. Before the Roman Empire, several maritime powers-the Greeks, Phoenicians, and Carthag;n;ans---colonized the Mediterranean coast. At the same time, the European interior saw Celtic princes establish control over most of Europe. During the second half of the first millennium B.C., the Celtic and maritime fiefdoms were each united by commercial, linguistic, and cultural ties, but were politically fragmented.
Ultimately, they would all fall to the Romans. 'TIle Romans built the first politically united culture in Europe, but it eventually fell to "barbarian" invaders from the East. The barbarians flourished, and only the eastern part of the Roman Empire-the Byzantine Empire-was to survive into the Middle Ages. Inthe west, Charlemagne founded the Holy Roman Empire in A.D. 800, the culmination ofFranldsh political development. France, Germany, and parts of Italy and Spain were briefly reunited. After A.D. 1000, Frankish power passed to Germany and, in part, to the Pope, although the
Papacy and the Empire were often in conflict. The Holy Roman Empire ceased to have any political importance by the fourteenth century, although Austrian emperors continued to take the title of Holy Roman Emperor until 1806. Several European states were formed or consolidated between 1000 !lnd 1500. Although wars among them were frequent, none was able to conquer much of Europe before Napoleon. With the development of seaworthy ships, the armies and navies qf Europeans attempted to extend their hegemony to the rest of the world, competing for national riches on other continents. The Portuguese, Spanish, English, Dutch, French, and Russians established overseas empires which would endure into the twentieth century, but in all of European history, not a single empire has lasted for more than five ~nturies. Napoleon rapidly conquered continental Europe, but his rule lasted for fewer than ten years.
The Chinese Empire began in the third century B.C. and endured many vicissitudes under myriad dynasties, none of which lasted for more than four centuries. After several difficult periOds, China fell to the Mongols in the thirteenth century. One hundred years later, the Ming restored Chinese dominance for three centuries. Then another foreign dynasty, the Qing, ruled for several centuries into the twentieth. The same pattern is found on every continent or subcontinent.
National pride is always more fervent in successful times. When a people feels strong, it is easier to say, 'We are the best.~ However, power can have ratller unusual origins. The wise decisions and shrewd political acts of a few leaders or small groups often produce endUring states. Even cruel regimes can sometimes succeed in introducing prosperous periods'. The rise to political power frequently requires violence, which is not always physical. Favorable external circumstances can also help maintain stability, if only temporarily. Politicians who wield their power responsibly are difficult to replace with equally capable successors. During happy and'prosperous years, people can convince themselves that their success is due to their excellent qualities, the intrinsic characteristics of their "race~ that make them great. The illusion of immortality ignores all the lessons