A group of blogs and Internet forums, led by blogger Steve Sailer, have come together to embrace a successor to the pseudoscientific racist movements of the 20th century. “Human biodiversity” (HBD) is the term they have used to give their particular theories a policy-wonk zing. (Read an in-depth explanation of the human biodiversity phenomenon here.) One of the hallmarks of HBD blogs is the use of data and charts from genetics studies to “prove” their theories. This evidence is culled from articles in the leading journals of population genetics and behavioral genetics, and published by some of genetics’ leading lights. But what does this evidence look like? And, if they’re using cutting-edge research to make their points, does that mean their theories hold some water?
We’ll start with the “evidence” itself. Most often it takes the form of what’s called a principal component analysis. A PCA is able to boil down a data set comprising hundreds or even thousands of dimensions (think the largest spreadsheet you’ve ever seen) into a 2D plot. (Or, depending on the type of analysis you’re running, 3D, or 4D, and so on.) If you do a PCA of a bunch of distinct genomes from around the world, you’ll get something that looks like this:
This PCA chart is from an article called “The population genetics of the Jewish people,” by Dr. Harry Ostrer and Dr. Karl Skorecki. Each individual dot represents one genome — one person’s DNA. The chart is just one of several data analysis methods they use for showing the genetic “location” of Jews — somewhere between Middle Eastern and European, as it turns out. The chart also shows, quite clearly, that all three of those populations are rather far away from the cluster of sub-Saharan African genomes.
This doesn’t, however, mean that sub-Saharan Africans are a different “race” from Jews. The chart is scaled so that differences between groups are enhanced: even though the two groups are far away from one another on the chart, the “distance” represents a very small amount of genetic variance. (And, if this chart included “New World” genomes, you would see much of the empty space taken up with a continuum of African American, Native American, Latino and Caribbean genomes.) Another kind of chart, called a neighbor-joining tree, (similar to a cladogram in evolutionary biology) also shows spatially the amount of variance between the genomes of certain populations, in order to discern the ancestry and descent of the different groups.
Geneticists use charts like these — that scale up, visually, the genetic differences between human populations — because they are interested in tracing the changes and mutations that happen at the level of a single trait, like eye color, or even a single nucleotide (the “building blocks” of DNA). Though a mutation on the scale of a single nucleotide might, for example, significantly increase your risk of getting Alzheimer’s disease, it doesn’t say much about your innate capabilities or faults as a member of a certain “race.”
HBDers can cite the data all they want: it just simply doesn’t say what they want it to say.