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FW: Genes, Peoples, and Languages, book review

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  • Popplestone, Ann
    ... From: ddunfee.. [mailto:ddunfee@CITY-NET.COM] Sent: Saturday, August 19, 2000 7:05 PM To: ANTHRO-L@LISTSERV.ACSU.BUFFALO.EDU Subject: Genes, Peoples, and
    Message 1 of 1 , Aug 21 1:20 PM
      FW: Genes, Peoples, and Languages, book review

      -----Original Message-----
      From: ddunfee.. [mailto:ddunfee@...]
      Sent: Saturday, August 19, 2000 7:05 PM
      To: ANTHRO-L@...
      Subject: Genes, Peoples, and Languages, book review

      today's ny times book reviewz:



                                                  GENES, PEOPLES, AND LANGUAGES
                    By Luigi Luca Cavalli-Sforza. Translated by Mark Seielstad.
                                                              228 pp. New York:
                                North Point Press/Farrar, Straus & Giroux. $24.


           A human being is a walking archive of historical evidence. Our
           ancestry as fishes shows up every time we choke. Our windpipes are
           in front of our throats, though our mouths are below our noses, and
           the absurd crossover from mouth to throat is evolutionarily
           descended from a sensible plumbing system in fish. But our genes
           are an even better source of historical evidence than our
           anatomies, and there is no better historical reader of our genes
           than Luigi Luca Cavalli-Sforza. In ''Genes, Peoples, and
           Languages,'' he says that in 1951 he began ''wondering whether it
           was possible to reconstruct the history of human evolution using
           genetic data from living populations.'' Since then he has invented
           a new way of studying human evolution.

           Cavalli-Sforza's research makes use of the global map of human
           genes. For instance, the A, B and O blood groups are under simple
           genetic control, and their frequencies have been measured all over
           the globe. The O blood group has a frequency of about 100 percent
           in South American Indians, about 50 percent in Northeast Asia and
           30-40 percent in Europe. There is a mass of evidence of this kind,
           collected over the past century. Cavalli-Sforza uses genetic
           differences among people from various places to reconstruct the
           ''tree'' of human evolution: a branching diagram of relations among
           different populations. He posits that populations that are
           genetically more similar probably share a more recent common
           ancestor than those that are genetically more distant. The results
           helped to establish a classic story: the common ancestor of all
           humans lived in Africa, about 70,000 to 100,000 years ago. Some
           Africans colonized Asia, and then Australia (55,000 years ago) and
           North America (maybe 30,000 years ago). About 40,000 years ago
           others from Africa, along with colonists from Asia, founded the
           European population of Homo sapiens and, probably, as they did so,
           eliminated the Neanderthals who had preceded them. Cavalli-Sforza,
           a geneticist at Stanford for many years, first produced a tree of
           human evolution in the 1960's. Indeed, he largely invented the
           idea, and it was not until the 80's that other scientists looked at
           the same question, using other kinds of genetic evidence. They have
           supported his main conclusions.

           His second big project looked at the spread of farming in Europe.
           Before it originated in the Middle East 10,000 years ago, humans
           were hunters and gatherers. But farming soon spread across Europe,
           in a great wave, from 9,000 to 6,000 years ago. Archaeologists used
           to think farming spread by cultural copying, as people imitated
           successful neighbors. Cavalli-Sforza suspected it might have spread
           because the farmers themselves moved, as the new practice led to
           higher population densities and subsequent migration. He tested the
           two ideas with genetic evidence. If the farmers moved, they would
           have taken their genes with them; but if the farming habit alone
           was copied, it would have had no genetic consequences. What he
           found was a gradient of genes across Europe, fanning out from the
           Middle East, and the gene map almost exactly matches the
           archaeological map of the spread of wheat. The movement of people,
           rather than the copying of a practice, caused the spread of
           farming. Cavalli-Sforza says that when he first published the work
           in 1984, it ''was not immediately welcomed by Anglo-American
           archaeologists.'' They are more welcoming now.

           Genes are a powerful source of historical evidence, but they are
           not bug-free. One problem is that humans form a genetic continuum.
           Evolutionary tree diagrams were invented to show relations between
           different species, like humans, chimpanzees and gorillas. A tree
           diagram for species makes clear sense; each branch in the diagram
           represents a distinct line of creatures. Within a species, the
           meaning of the branches is less clear and can even be bogus. If
           chimpanzees were a genetic mix, resulting from repeated
           interbreeding between gorillas and humans, it would be odd to
           represent their evolution by one branch leading off the human line
           of the tree. The reality would be a blurry mess. But that is
           exactly what ancestral relations are like within the human species.
           It is difficult to say what a tree means when its branches are
           within one species, and Cavalli-Sforza says little about that

           He says more about the related question of human races. One
           misinterpretation of a human evolutionary tree would be that it
           shows the branching off of distinct races, with separate histories.
           A major achievement of human genetics has been exploding the theory
           that races are genetically distinct. They are genetically only
           skin-deep: races do differ in a small number of genes that
           influence superficial features like skin color. But the great
           majority of our genes are a mish-mash and do not fall into any
           discrete subcategories of human being. Cavalli-Sforza shows that
           the European population is the most genetically mixed-up on earth,
           being a mix of genes from Asia and Africa. He uses this to poke fun
           at Arthur de Gobineau, the 19th-century French author of the
           ''Essay on the Inequality of Human Races,'' which helped inspire
           German racism. De Gobineau, he says, ''would die of rage and shame
           at this suggestion since he believed that Europeans . . . were the
           most genetically pure race, the most intellectually gifted and the
           least weakened by racial mixing.''

           Right on! But I should have liked Cavalli-Sforza to tell us more
           about what these mix-ups mean for the branches on his evolutionary

           The book is written for nonspecialists. It contains some technical
           terms, but they are well flagged. Readers can easily fast-forward
           through them. It is also a personal book, almost amounting to an
           intellectual autobiography. Cavalli-Sforza describes his own work
           on cultural evolution but ignores the work of other scientists. He
           describes his own research on the ''great diasporas,'' like the
           spread of farming, but ignores another method that has been used.
           He describes his own reconstruction of human evolution but does
           little more than mention complementary research that uses
           mitochondrial DNA. However, the personal style of the book makes it
           more readable than a balanced survey could hope to be. And
           Cavalli-Sforza has himself contributed so much to the subject in
           the past half-century that he is the ideal author for a personal
           account of it.

           Mark Ridley is a lecturer in the department of zoology at the
           University of Oxford.
         Copyright 2000 The New York Times Company

      "Nothing needs so reforming as other people's habits." -- Mark Twain

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