Depictions of human genetic relationships

Science writer, Nicholas Wade, and philosopher Nevan Sesardic, among others have argued that Rosenberg et al’s division of human genetic diversity into reasonably distinct clusters (depicted as bands of color in their diagrams) shows that human racial divisions have a biological basis after all.  Some lines of critical inquiry that I would recommend:

  1. What, if anything, follows if researchers are able to assign individuals to a cluster carved out all the continuum of genetic variation among humans? The following issues (and others) are pertinent: The method of clustering does not ensure that all genetic variation maps onto the clusters. It could be, for example, that there is variation within clusters for most of the loci even though clusters can be distinguished on a particular set of loci. Wade and Sesardic want some kind of racial classification to provide, because it corresponds to these clusters, explanations of average differences among races in some kinds of socially meaningful traits. It is not clear how they could adjudicate between their genetic (“biological”) explanations and social explanations (in which unequal treatment according to racially labeled groups leads to differences in health and behavioral outcomes). Given that individuals vary in their position within a cluster, it is not clear how average differences help anyone decide how to treat an individual. For elaboration, see my 2011 commentary on Sesardic (2010).
  1. Can any depiction of genetic relationships among humans allow simultaneously for similarity, diversity, ancestry, and admixture (i.e., groups that had split mixing again)? See my sequence of blog posts exploring this, starting from In this vein, for example, does the colored band privilege racialist views by, for example, focusing on variation and not similarity according to relatedness by lineages of descent?
  1. Would an analysis of the argumentation practices of Wade and/or Sesardic show places where they are open to reconsidering their conclusions? (Sesardic is a critic of positions accepted by liberal-left philosophers about heritability, genes, IQ test scores, and racial differences. The theme that recurs in his criticisms is that philosophers need to delve more deeply into the science as they consider their arguments. I have not seen him delve any deeper than what seems convenient for his positions—but I have not studied his corpus carefully.)   If so, what would be the key issues of language and graphic representation to tackle? If not, what other audiences need to be addressed, and in what ways, to help them avoid transforming science into arguments for the biological basis of race.


Rosenberg, NA, JK Pritchard, JL Weber, HM Cann, KK Kidd, LA Zhivotovsky and MW Feldman (2002). Genetic structure of human populations. Science 298: 2381-2385. Sesardic N (2010) Race: A Social Destruction of a Biological Concept. Biology and Philosophy 25:143-162.
Taylor, P. J. (2011) ”Rehabilitating a biological notion of race? A response to Sesardic,” Biology and Philosophy, 26 (3):469-473.
Wade, N. (2014). A troublesome inheritance: Genes, race and human history. New York: The Penguin Press


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