Before shooting ten African-American people in Buffalo on May 14, 2022, supremacist Payton Gendron published a manifesto: 180 delirious pages on the “great replacement” and anti-Semitic conspiracy theories, in which we also find published genomic studies in prestigious journals. What revive fears that current work in genetics endorse the return of “races” in science.
“We cannot categorize ‘races’ on the basis of genetics”, slice Lluis Quintana-Murci, professor at the Collège de France and researcher at the Institut Pasteur. “In dogs, breeds exist. These are groups with strong genetic differences between them, but with very few differences within them. In humans, the groups are not very distinct. There are thus very few differences between ethnic groups, while the greatest difference is found between individuals of the same group”, assures the author of the essential people of humans (Odile Jacob).
In recent years, major international genomic studies have confirmed that most genetic variability is observed within given populations, with little genetic difference between them. This result can be explained by interbreeding, and by the fact that human groups have never evolved in complete isolation. No mutation specific to a geographical region is thus found in 100% of the individuals of a given population, and nowhere else. For Quintana-Murci, human populations, marked by multiple mixing, represent “a continuum of genetic variability”. Testifying to successive migrations, these variations are strongest in sub-Saharan Africa, the cradle of humanity, and decrease as one moves away from it.
“Race”, an ideological construct
In The Genetic Lottery, Kathryn Paige Harden, professor at the University of Texas, emphasizes the importance of distinguishing “race”, a social and ideological construction, from “ancestry”, used in genetics to designate a person’s origins. The racial categories were fixed arbitrarily, according to a socio-historical context, with the idea that they would be perfectly distinct and hierarchical. Because of the segregationist rule of “one drop of blood”, anyone with only one ancestor from sub-Saharan Africa was considered “black”, while those who identify today as “Black or Afro- Americans” in the United States exhibits vast genetic diversity.
Skin pigmentation, size, metabolization of certain foods, differences in infectious diseases… The diversity of phenotypic traits is, in large part, the result of natural selection, populations having had to adapt locally to their particular environments. An environmental and cultural diversity that is reflected in genetic variation and explains why GWAS, or genome-wide association studies, may have some predictive value for a given population, but less so for others. However, this research has a strong Eurocentric bias. “Today, we explain 40 to 45% of the variations in height in a population of European ancestry, but we have four times less precision for an African population”, testifies Loïc Yengo, statistician at the University of Queensland (Australia ). For scientific, medical and societal reasons, Kathryn Paige Harden or Lluis Quintana-Murci call for the rapid diversification of these genomic studies. It would also be the best way to respond to fantasized comparisons between populations, regularly brandished by far-right circles (like a supposed “world map of IQs”), but which have no scientific basis.