I have previously scoffed against race realism and related topics in a few blog posts.
The Youtube user C0nc0rdance (Youtube channel, blog) has made a set of two videos explaining the scientific flaws of race realism called “The Science of Human Races” (part 1, part 2) that I find very convincing. Consider this a summary of the arguments and evidence put forward (although c0nc0rdance might not have used the exact sources I list), with some personal comments from me and links or references to the primary scientific literature when possible. This list is also not necessarily chronological.
The first part provides a strong and forceful refutation of race realism, looking at stuff like haplogroups, principle component analysis and genetic population substructure.
|Divisions of human diversity into essentialist biological categories has no scientific merit. Such categories are arbitrary and not more meaningful than any other division of human diversity.
||Jews, although traditionally considered to be an essentialist biological category, actually consists of around eight subpopulations whose genetics overlap with populations that are not Jewish (Behar et. al. 2010).
There are at least 56 ethnic groups in China (Lilly, 2009) but race realists would presumably lump them together with other Asians into one traditional racial category.
|There may be biological underpinnings for some human categories, but this is not what people use when assigning individuals into racial categories. Simplistic racial categories do not accurately reflect actual biological diversity.
||Cases where identical twin can have different skin color and placed into separate racial categories (Donaldsson James, 2009; Moorhead, 2011).
The fact that African-Americans often score higher than the European population markers than European-Americans (Parra et. al., 2004). African-Americans can have 5-20% European population markers due to admixture.
A sizable proportion of the time (~1/3), a person is more phenotypically similar to someone of a different population than one of a similar population (Witherspoon et. al. 2007).
The fact that traditional racial categories do not form monophyletic clades.
|Haplogroups use biological markers, but you cannot determine what haplogroup a person will belong to simply by looking at them. Haplogroups do not justify traditional racial categories.
||World haplogroup maps use STRs and MtDNA (McDonald, 2005).
|Humans have a fairly low genetic population substructure.
||It is around 0.11. (Templeton, 1998), so 89% of all variation in humans is shared among all groups. According to S. Wright, the cut-off for the existence of subspecies is be 0.25.
|The use of PCA to demonstrate race realism is invalid, as the discontinuity is a result of sampling, not the existence of discrete races.
The change in inferred populations (K) affects the number of clusters. What is not changing is the data. The data does not uniquely specify K.
|Sampling populations in between shows more of a continuous change, with the exception of larger geographical separations (Watkins, 2003; Serre and Pääbo, 2004). This suggest human diversity is better described by a cline (continuous distribution of alleles) than races, subspecies or demes.
The second part goes into more details with regards to how human diversity arose and and discusses possible explanations for why certain African countries are overrepresented in the statistics of Olympic medals. However, I will focus more on the arguments against race realism. If you want to know more about possible explanations for why some African countries are really good at e. g. sprinting, watch the video.
|With rare exceptions, human populations are not completely isolated and there has been a lot of gene flow between various populations. In other words, humans span the globe with little geographical isolation (cf. argument about cline). There are almost no pure populations.
||World-wide distribution of some haplogroups, such as haplogroup Q that exists in North and South America, Africa and Europe (McDonald, 2005).
Geographically close populations overlap in PCA graphs (Watkins, 2003; Serre and Pääbo, 2004).
Southern Europeans have 1-3% African ancestry in the recent past. (Moorjani, 2011).
Afro-Caribbeans have about 11% European ancestry and about 3% Native American ancestry (Stefflova et. al. 2011).
Waterfall graphs display a lot of admixture (Xing, 2010). When a larger number of inferred groups is allowed (i .e. higher value of K), almost no population is entirely pure.
|Differential natural selection has not been a major force in producing traditional racial categories, with a few exceptions. Rather, founder effects and genetic drift have been more important.
||There are only a few alleles that have undergone recent positive selection to be classified as high-Fst alleles and these are mostly relevant things like skin color, hair texture, immunological function (Barreiro et. al. 2008; Laland et. al. 2010).
Most environments would probably select for intelligence and athletic ability.
|Statistical differences among groups need not be relevant or meaningful.
||Correlation does not imply causation.
Left-handed people perform worse on nearly all outcomes measured (Johnston et. al. 2009), but this doesn’t mean much as it lacks biological plausibility.
|Racial medicine is not necessarily reasonable.
||The Nitric oxide synthase G89T4 single-nucleotide polymorphism that contributes to arterial stiffness has only a 20% difference in frequency between African-Americans and European-Americans (Chen, 2004). Most African-Americans would not get any additional benefit from the drug marketed to African-Americans and some European-Americans would benefit from it.
Might as well test for the presence of that SNP in the first place, replacing racial medicine with individualized medicine. Self-described traditional race category is a poor approximation.
There where some interesting arguments relevant for debunking race realism that I did not bring up in this summary because I was unable to either locate or understand the relevant reference.
Barreiro, L. B., Laval, G., Quach, H., Patin, E., & Quintana-Murci, L. (2008). Natural selection has driven population differentiation in modern humans. [10.1038/ng.78]. Nat Genet, 40(3), 340-345.
Behar, D. M., Yunusbayev, B., Metspalu, M., Metspalu, E., Rosset, S., Parik, J., . . . Villems, R. (2010). The genome-wide structure of the Jewish people. Nature, 466(7303), 238-242.
Chen, W., Srinivasan, S. R., Bond, M. G., Tang, R., Urbina, E. M., Li, S., . . . Berenson, G. S. (2004). Nitric oxide synthase gene polymorphism (G894T) influences arterial stiffness in adults. Am J Hypertens, 17(7), 553-559.
Donaldson James, S. (2011). Twins Born: One Black, One White. ABC News. Accessed: 2012-08-18.
Johnston, D. W., Nicholls, E. R., Shah, M., Shields, M. A. (2009). Nature’s Experiment? Handedness and Early Childhood Development. Demography. 2009 May; 46(2): 281–301.
Laland, K. N., Odling-Smee, J., & Myles, S. (2010). How culture shaped the human genome: bringing genetics and the human sciences together. Nat Rev Genet, 11(2), 137-148.
Lilly, A. (2009). A Guide to China’s Ethnic Groups. Washington Post. Accessed: 2012-08-18.
McDonald, J. D. (2005). World Haplogroups Maps. Accessed: 2012-08-18.
Moorhead, J. (2011). Black and white twins. The Guardian. Accessed: 2012-08-18.
Moorjani, P., Patterson, N., Hirschhorn, J. N., Keinan, A., Hao, L., Atzmon, G., . . . Reich, D. (2011). The History of African Gene Flow into Southern Europeans, Levantines, and Jews. PLoS Genet, 7(4), e1001373. doi: 10.1371/journal.pgen.1001373
Parra, E. J., Kittles, R. A., & Shriver, M. D. (2004). Implications of correlations between skin color and genetic ancestry for biomedical research. Nat Genet. S54-S60.
Serre, D., & Pääbo, S. (2004). Evidence for Gradients of Human Genetic Diversity Within and Among Continents. Genome Research, 14(9), 1679-1685. doi: 10.1101/gr.2529604
Stefflova, K., Dulik, M. C., Barnholtz-Sloan, J. S., Pai, A. A., Walker, A. H., & Rebbeck, T. R. (2011). Dissecting the Within-Africa Ancestry of Populations of African Descent in the Americas. PLoS ONE, 6(1), e14495. doi: 10.1371/journal.pone.0014495
Templeton, A. R. (1998). Human Races: A Genetic and Evolutionary Perspective. American Anthropologist, 100(3), 632-650. doi: 10.1525/aa.19188.8.131.522
Watkins, W. S., Rogers, A. R., Ostler, C. T., Wooding, S., Bamshad, M. J., Brassington, A.-M. E., . . . Jorde, L. B. (2003). Genetic Variation Among World Populations: Inferences From 100 Alu Insertion Polymorphisms. Genome Research, 13(7), 1607-1618. doi: 10.1101/gr.894603
Witherspoon, D. J. Wooding, S. Rogers, A. R. Marchani, E. E. Watkins, W. S. Batzer, M. A. and Jorde, L. B. (2007). Genetic Similarities Within and Between Human Populations. Genetics. 176(1): 351–359.
Xing, J., Watkins, W. S., Shlien, A., Walker, E., Huff, C. D., Witherspoon, D. J., . . . Jorde, L. B. (2010). Toward a more uniform sampling of human genetic diversity: A survey of worldwide populations by high-density genotyping. Genomics, 96(4), 199-210. doi: 10.1016/j.ygeno.2010.07.004