Lewontin’s Fallacy: More Genetic Variation Within Races Than Between Them? Part III
Human Evolutionary Change 100 Times Higher in Past 5,000 Years - Findings Suggest We Are Becoming More Different, Not Alike
This book’s main thesis is that human civilisation greatly accelerated increases in the rates of evolution. The authors criticise the accepted conventional wisdom that says the evolutionary process stopped when modern humans first appeared.
Gene variants that were under strong selection (reached fixation) over the last 10k years are different in different [races] clusters. That is, the way that modern people in each cluster differ, due to natural selection, from their own ancestors 10k years ago is not the same in each cluster — we have been, at least at the genetic level, experiencing divergent evolution. In fact, recent research suggests that 7% or more of all our genes are mutant versions that replaced earlier variants through natural selection over the last tens of thousands of years:
Recent acceleration of human adaptive evolution:
Using the 3.9-million HapMap SNP dataset, we found that selection has accelerated greatly during the last 40,000 years. Larger populations generate more new selected mutations, and we show the consistency of the observed data with the historical pattern of human population growth. We consider human demographic growth to be linked with past changes in human cultures and ecologies.
The method they used looks for regions of DNA with similar SNP patterns. If an advantageous gene swept through a population in a relatively short time, replacing other variants, then the pattern of nucleotide polymorphisms in that area of the chromosome will be particularly uniform throughout the group. The results imply that we are all descended from mutants who, relatively recently, out-competed and replaced their contemporaries. The distribution of mutations is not uniform in different geographical populations (races). Recent evolution is causing genetic divergence, not convergence.
University of Utah Press Release for the above study:
Researchers discovered genetic evidence that human evolution is speeding up - and has not halted or proceeded at a constant rate, as had been thought - indicating that humans on different continents are becoming increasingly different.
"We used a new genomic technology to show that humans are evolving rapidly, and that the pace of change has accelerated a lot in the last 40,000 years, especially since the end of the Ice Age roughly 10,000 years ago,” says research team leader Henry Harpending, a distinguished professor of anthropology at the University of Utah.
"We aren’t the same as people even 1,000 or 2,000 years ago," he says, which may explain, for example, part of the difference between Viking invaders and their peaceful Swedish descendants. "The dogma has been these are cultural fluctuations, but almost any Temperament trait you look at is under strong genetic influence.”
"Human races are evolving away from each other," Harpending says. "Genes are evolving fast in Europe, Asia and Africa, but almost all of these are unique to their continent of origin. We are getting less alike, not merging into a single, mixed humanity.”
The increase in human population from millions to billions in the last 10,000 years accelerated the rate of evolution because "we were in new environments to which we needed to adapt," Harpending adds. “And with a larger population, more mutations occurred.”
The bottom image of this post exemplifies the prediction of continental origin using randomly selected markers, as discussed above.
- "Race Is A Social Construct"
Race as something completely socially constructed is disproven by the fact that socially constructed race is correlated with physical characteristics. Thus, rather than being separated from biology, the social phenomenon of race is rooted in biology.
A different argument holds that race is correlated with biology, but the differences are "skin-deep", e.g, involve only superficial, visible, (and by some strange logic unimportant characteristics). According to the proponents of this view, the idea of biological race places an undue emphasis on a set of traits: it is a result of the subjective choice of a set of traits as race-defining. Thus, the commonly recognized races of traditional physical anthropology are discounted as subjective organizations of the biological data: we could just as simply speak of a "lactose-intolerant race" according to this view.
The new paper is one of many recent papers that have discovered that no matter what genetic markers you choose: SNPs, STRs, no matter how you choose them: randomly or based on their “informativeness”, it is relatively easy to classify DNA into the correct continental origin. Depending on the marker types (e.g., indel vs. microsatellite), and their informativeness (roughly the distribution differences between populations), one may require more or less markers to achieve a high degree of accuracy. But, the conclusion is the same: after a certain number of markers, you always succeed in classifying individuals according to continental origin.
The structuring of humanity into more or less disjoint groups is not a subjective choice: it emerges naturally from the genomic composition of humans, irrespective of how you study this composition. Rather than proving that race is skin-deep, non-existent, or unimportant, modern genetic science is both proving that it is in fact existent, but also sets the foundation for the study of its true importance, particularly in regards to medicine.
Geography and genography: prediction of continental origin using randomly selected single nucleotide polymorphisms:
The genetic differences between continentally defined groups are sufficiently large that one can accurately predict ancestral continent of origin using only a minute, randomly selected fraction of the genetic variation present in the human genome.
Conclusion: Accurate characterization of ancestry is possible using small numbers of randomly
selected SNPs. The results presented here show how investigators conducting genetic association studies can use small numbers of arbitrarily chosen SNPs to identify stratification in study subjects and avoid false positive genotype-phenotype associations. Our findings also demonstrate the extent of variation between continentally defined groups and argue strongly against the contention that genetic differences between groups are too small to have biomedical significance.