Lewontin's Fallacy
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"Human Genetic Diversity: Lewontin's Fallacy" is a 2003 paper by A. W. F. Edwards. He criticises an argument first made in Richard Lewontin's 1972 article " The Apportionment of Human Diversity", that the practice of dividing humanity into races is
taxonomically In biology, taxonomy () is the scientific study of naming, defining ( circumscribing) and classifying groups of biological organisms based on shared characteristics. Organisms are grouped into taxa (singular: taxon) and these groups are given ...
invalid because any given individual will often have more in common genetically with members of other population groups than with members of their own. Edwards argued that this does not refute the biological reality of race since genetic analysis can usually make correct inferences about the perceived race of a person from whom a sample is taken, and that the rate of success increases when more genetic loci are examined. Edwards' paper was reprinted, commented upon by experts such as
Noah Rosenberg Noah Aubrey Rosenberg is a geneticist working in evolutionary biology, human genetics, and population genetics, now Professor at Stanford University. His research is concerned with quantifiable changes in the human genome over time, and he is famou ...
, and given further context in an interview with philosopher of science Rasmus Grønfeldt Winther in a 2018 anthology. Edwards' critique is discussed in a number of academic and
popular science ''Popular Science'' (also known as ''PopSci'') is an American digital magazine carrying popular science content, which refers to articles for the general reader on science and technology subjects. ''Popular Science'' has won over 58 awards, incl ...
books, with varying degrees of support. Some scholars, including Winther and Jonathan Marks, dispute the premise of "Lewontin's fallacy", arguing that Edwards' critique does not actually contradict Lewontin's argument. A 2007 paper in '' Genetics'' by David J. Witherspoon et al. concluded that the two arguments are in fact compatible, and that Lewontin's observation about the distribution of genetic differences across ancestral population groups applies "even when the most distinct populations are considered and hundreds of loci are used".


Lewontin's argument

In the 1972 study " The Apportionment of Human Diversity", Richard Lewontin performed a fixation index (''F''ST) statistical analysis using 17 markers, including blood group proteins, from individuals across classically defined "races" (Caucasian, African, Mongoloid, South Asian Aborigines, Amerinds, Oceanians, and Australian Aborigines). He found that the majority of the total genetic variation between humans (i.e., of the 0.1% of DNA that varies between individuals), 85.4%, is found within populations, 8.3% of the variation is found between populations within a "race", and only 6.3% was found to account for the racial classification. Numerous later studies have confirmed his findings. Based on this analysis, Lewontin concluded, "Since such racial classification is now seen to be of virtually no genetic or taxonomic significance either, no justification can be offered for its continuance." This argument has been cited as evidence that racial categories are biologically meaningless, and that behavioral differences between groups are not caused by genetic differences. One example is the "Statement on 'Race'" published by the
American Anthropological Association The American Anthropological Association (AAA) is an organization of scholars and practitioners in the field of anthropology. With 10,000 members, the association, based in Arlington, Virginia, includes archaeologists, cultural anthropologists, ...
in 1998, which rejected the existence of races as unambiguous, clearly demarcated, biologically distinct groups.


Edwards' critique

Edwards argued that while Lewontin's statements on variability are correct when examining the frequency of different alleles (variants of a particular gene) at an individual locus (the location of a particular gene) between individuals, it is nonetheless possible to classify individuals into different racial groups with an accuracy that approaches 100 percent when one takes into account the frequency of the alleles at several loci at the same time. This happens because differences in the frequency of alleles at different loci are correlated across populations—the alleles that are more frequent in a population at two or more loci are correlated when we consider the two populations simultaneously. Or in other words, the frequency of the alleles tends to cluster differently for different populations. In Edwards' words, "most of the information that distinguishes populations is hidden in the correlation structure of the data". These relationships can be extracted using commonly used ordination and
cluster analysis Cluster analysis or clustering is the task of grouping a set of objects in such a way that objects in the same group (called a cluster) are more similar (in some sense) to each other than to those in other groups (clusters). It is a main task of ...
techniques. Edwards argued that, even if the probability of misclassifying an individual based on the frequency of alleles at a single locus is as high as 30% (as Lewontin reported in 1972), the misclassification probability becomes close to zero if enough loci are studied. Edwards' paper stated that the underlying logic was discussed in the early years of the 20th century. Edwards wrote that he and Luigi Luca Cavalli-Sforza had presented a contrasting analysis to Lewontin's, using very similar data, already at the 1963
International Congress of Genetics The International Congress of Genetics (ICG) is a five yearly conference for geneticists. The first ICG was held in 1898. Since 1973 It has been organized by the International Genetics Federation (IGF). The aim of the congress is to reflect on prog ...
. Lewontin participated in the conference but did not refer to this in his later paper. Edwards argued that Lewontin used his analysis to attack human classification in science for social reasons.


Support and criticism

Evolutionary biologist
Richard Dawkins Richard Dawkins (born 26 March 1941) is a British evolutionary biologist and author. He is an emeritus fellow of New College, Oxford and was Professor for Public Understanding of Science in the University of Oxford from 1995 to 2008. An ath ...
discusses genetic variation across human races in his book '' The Ancestor's Tale''. In the chapter "The Grasshopper's Tale", he characterizes the genetic variation between races as a very small fraction of the total human genetic variation, but he disagrees with Lewontin's conclusions about taxonomy, writing: "However small the racial partition of the total variation may be, if such racial characteristics as there are highly correlate with other racial characteristics, they are by definition informative, and therefore of taxonomic significance."
Neven Sesardić Neven Sesardić (born 30 July 1949) is a Croatian philosopher known for his writings on heritability and race who worked most of his career as a professor at Lingnan University in Hong Kong. Life and career He grew up in communist Yugoslavia ...
has argued that, unbeknownst to Edwards, Jeffry B. Mitton had already made the same argument about Lewontin's claim in two articles published in '' The American Naturalist'' in the late 1970s. Biological anthropologist
Jonathan M. Marks Jonathan M. Marks (born 1955) is a professor of biological anthropology at the University of North Carolina at Charlotte. He is a significant figure in anthropology, especially on the topic of race. Marks is skeptical of genetic explanations of h ...
agrees with Edwards that correlations between geographical areas and genetics obviously exist in human populations but goes on to write:
What is unclear is what this has to do with 'race' as that term has been used through much in the twentieth century—the mere fact that we can find groups to be different and can reliably allot people to them is trivial. Again, the point of the theory of race was to discover large clusters of people that are principally homogeneous within and heterogeneous between, contrasting groups. Lewontin's analysis shows that such groups do not exist in the human species, and Edwards' critique does not contradict that interpretation.
The view that while geographic clustering of biological traits does exist, this does not lend biological validity to racial groups, was proposed by several evolutionary anthropologists and geneticists prior to the publication of Edwards' critique of Lewontin. In the 2007 paper "Genetic Similarities Within and Between Human Populations", Witherspoon et al. attempt to answer the question "How often is a pair of individuals from one population genetically more dissimilar than two individuals chosen from two different populations?" The answer depends on the number of polymorphisms used to define that dissimilarity, and the populations being compared. When they analysed three geographically distinct populations (European, African, and East Asian) and measured
genetic similarity Genetic distance is a measure of the genetic divergence between species or between populations within a species, whether the distance measures time from common ancestor or degree of differentiation. Populations with many similar alleles have sma ...
over many thousands of loci, the answer to their question was "never"; however, measuring similarity using smaller numbers of loci yielded substantial overlap between these populations. Rates of between-population similarity also increased when geographically intermediate and admixed populations were included in the analysis. Witherspoon et al. write:
Since an individual's geographic ancestry can often be inferred from his or her genetic makeup, knowledge of one's population of origin should allow some inferences about individual genotypes. To the extent that phenotypically important genetic variation resembles the variation studied here, we may extrapolate from genotypic to phenotypic patterns. ... However, the typical frequencies of alleles responsible for common complex diseases remain unknown. The fact that, given enough genetic data, individuals can be correctly assigned to their populations of origin is compatible with the observation that most human genetic variation is found within populations, not between them. It is also compatible with our finding that, even when the most distinct populations are considered and hundreds of loci are used, individuals are frequently more similar to members of other populations than to members of their own population. Thus, caution should be used when using geographic or genetic ancestry to make inferences about individual phenotypes.
Witherspoon et al. add: "A final complication arises when racial classifications are used as proxies for geographic ancestry. Although many concepts of race are correlated with geographic ancestry, the two are not interchangeable, and relying on racial classifications will reduce predictive power still further." In a 2014 paper, reprinted in the 2018 Edwards Cambridge University Press volume, Rasmus Grønfeldt Winther argues that "Lewontin's fallacy" is effectively a misnomer, as there really are two different sets of methods and questions at play in studying the genomic population structure of our species: "variance partitioning" and "clustering analysis". According to Winther, they are "two sides of the same mathematics coin" and neither "necessarily implies anything about the ''reality'' of human groups".


See also

* Race and genetics * Population groups in biomedicine


References

{{DEFAULTSORT:Human Genetic Diversity: Lewontin's Fallacy Biology papers Human population genetics Race (human categorization) Biology controversies Taxonomy (biology) 2003 in biology 2003 works Criticism of individuals