Book Review

The Great Human Diasporas: The history of diversity and evolution

N Engl J Med 1996; 334:409-410February 8, 1996

Article

The Great Human Diasporas: The history of diversity and evolution
By Luigi Luca Cavalli-Sforza and Francesco Cavalli-Sforza. 300 pp. Reading, Mass., Addison–Wesley, 1995. $27.50. ISBN: 0-201-40755-8

In this easy-to-read book for nonspecialists, L. Luca Cavalli-Sforza and his son Francesco tell the story of human diversity through an overview of the 40-year work of the elder Cavalli-Sforza. In contrast to The Bell Curve (R.J. Herrnstein and C. Murray. New York: Free Press, 1994), which has been scrutinized scientifically and politically for its account of genetic variation and racial differences in IQ, The Great Human Diasporas is a refreshing celebration of differences among humans.

L. Luca Cavalli-Sforza is primarily a population geneticist, whose collaborations with anthropologists, archeologists, and linguists have brought unparalleled richness to the study of evolution and variation among humans. The first chapter, on African Pygmies, provides a glimpse of his dedication to multidisciplinary research. His cultural studies of this population offer a look into life in a hunter–gatherer society. The characterization of the mating structure of Pygmy society defines the forces that maintain genetic diversity, and the study of physical attributes reveals accommodations to environmental pressures. This is the most personal chapter of the book, containing asides on the many difficulties of research. These anecdotes serve well to highlight the elder Cavalli-Sforza's creative approach to a branch of science in which experimentation cannot be used.

The remainder of the book is broader in scope and can be roughly divided into four sections, covering the evolution of Homo sapiens, genetic differences among modern humans, linguistic and cultural evolution, and current issues of human diversity, including racism, bioethics, and abortion. Overviews of the technical details of topics such as carbon dating, DNA and the mechanisms of inheritance, and the estimation of heritability are scattered throughout, allowing lay readers to grasp the general themes. These descriptions can be easily skipped by those with sufficient background.

The four general sections could stand alone, but their union makes the book unique. Indeed, together they deliver the principal message — that it is the biologically based abilities of all humans that have led to cultural and linguistic diversity. As the authors ably demonstrate, cultural and linguistic differences between populations do, in some cases, parallel genetic differences; in other cases, however, they clearly do not. The Cavalli-Sforzas reiterate this point in the chapter on race and racism, noting that cultural ties within a nation can be dangerously confused with the notion of racial purity. This idea is quickly put to rest through the authors' discussion of genetic variation within populations and the importance of maintaining this variation as a critical weapon against future environmental challenges.

The book concludes with a postscript, added since the initial publication in 1993, in Italian. Here, the authors respond to The Bell Curve and challenge Herrnstein and Murray on specific points, maintaining that they overestimate the heritability of IQ and confuse racial differences with genetic differences in IQ. More generally, the Cavalli-Sforzas question the view of intelligence that limits it to IQ, ignoring other talents that bring richness to human culture. This section too could stand alone, but it seems fitting to include it at the end of the book, after the reader has pondered the beauty of diversity and the evolution of genes and culture together.

A few limitations should be noted. This book is clearly an account of L. Luca Cavalli-Sforza's research program and contains few explicit references to the work of those outside his circle. For example, little attention is paid to the vast literature on behavioral genetics. Also, the reader should be prepared to find the author's personal reflections on ethical issues scattered throughout the book, with particular attention paid to abortion and the position of the Roman Catholic Church. Since the book is written for nonspecialists, readers interested in scientific rigor will have to go elsewhere. For students of population genetics, the Cavalli-Sforzas' seminal discussions of the topic are a good place to start.

Joanne M. Meyer, Ph.D.
Virginia Commonwealth University, Richmond, VA 23219