Patterns of Human Diversity, within and among Continents, Inferred from Biallelic DNA Polymorphisms

  1. Chiara Romualdi1,2,7,
  2. David Balding3,8,
  3. Ivane S. Nasidze4,
  4. Gregory Risch5,
  5. Myles Robichaux5,
  6. Stephen T. Sherry5,
  7. Mark Stoneking4,
  8. Mark A. Batzer5,6, and
  9. Guido Barbujani1,9
  1. 1 Department of Biology, University of Ferrara, Ferrara I-44100, Italy; 2 Department of Statistics, University of Padua, Padua I-35121, Italy; 3 Department of Applied Statistics, University of Reading, Reading RG6 6FN, United Kingdom; 4 Max Planck Institute for Evolutionary Anthropology, Leipzig, D-04103 Germany; 5Department of Pathology, Stanley S. Scott Cancer Center, Louisiana State University Health Sciences Center, New Orleans, Louisiana 70112, USA; 6Department of Biological Sciences, Biological Computation and Visualization Center, Louisiana State University, Baton Rouge, Louisiana 70803, USA

Abstract

Previous studies have reported that about 85% of human diversity at Short Tandem Repeat (STR) and Restriction Fragment Length Polymorphism (RFLP) autosomal loci is due to differences between individuals of the same population, whereas differences among continental groups account for only 10% of the overall genetic variance. These findings conflict with popular notions of distinct and relatively homogeneous human races, and may also call into question the apparent usefulness of ethnic classification in, for example, medical diagnostics. Here, we present new data on 21 Alu insertions in 32 populations. We analyze these data along with three other large, globally dispersed data sets consisting of apparently neutral biallelic nuclear markers, as well as with a β-globin data set possibly subject to selection. We confirm the previous results for the autosomal data, and find a higher diversity among continents for Y-chromosome loci. We also extend the analyses to address two questions: (1) whether differences between continental groups, although small, are nevertheless large enough to confidently assign individuals to their continent on the basis of their genotypes; (2) whether the observed genotypes naturally cluster into continental or population groups when the sample source location is ignored. Using a range of statistical methods, we show that classification errors are at best around 30% for autosomal biallelic polymorphisms and 27% for the Y chromosome. Two data sets suggest the existence of three and four major groups of genotypes worldwide, respectively, and the two groupings are inconsistent. These results suggest that, at random biallelic loci, there is little evidence, if any, of a clear subdivision of humans into biologically defined groups.

Footnotes

  • Present addresses: 7CRIBI, Biotechnology Centre, University of Padua, Padua I-35121 Italy; 8Department of Epidemiology and Public Health, Imperial College, St. Mary's campus, Norfolk Place, London W2 1PG, United Kingdom.

  • 9 Corresponding author. University of Ferrara, Department of Biology, via L. Borsari 46, I-44100 Ferrara, Italy

  • E-MAIL bjg{at}unife.it; FAX (+39) 0532 249761.

  • Article and publication are at http://www.genome.org/cgi/doi/10.1101/gr.214902.

    • Received September 18, 2001.
    • Accepted February 12, 2002.
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