Abstract: Human populations living in Eurasia during the Holocene experienced significant evolutionary change. It has been predicted that the transition of Holocene populations into agrarianism and urbanization brought about culture-gene co-evolution that favoured via directional selection genetic variants associated with higher general cognitive ability (GCA). Population expansion and replacement has also been proposed as an important source of GCA gene-frequency change during this time period. To examine whether GCA might have risen during the Holocene, we compare a sample of 99 ancient Eurasian genomes (ranging from 4,557 to 1,208 years of age) with a sample of 503 modern European genomes, using three different cognitive polygenic scores. Significant differences favouring the modern genomes were found for all three polygenic scores (Odds Ratio=0.92, p=0.037; 0.81, p=0.001 and 0.81, p=0.02). Furthermore, a significant increase in positive allele count over 3,249 years was found using a sample of 66 ancient genomes (r=0.217, p one-tailed=0.04). These observations are consistent with the expectation that GCA rose during the Holocene.As far as I can see, the preprint overall makes sense, and this part is interesting in the context of population genetics, even if it just confirms what many of us here have already known.
Late Bronze Age European and Central Asian gene pools resemble present-day Eurasian genetic structure (17). Indeed, with values of Fst ranging from 0.00 to 0.08, the genetic distances between present-day European 1000 Genomes samples and the Ancient samples indicate little to modest levels of genetic differentiation (little differentiation corresponds to an Fst range of 0 to 0.05, and modest to an Fst range of 0.05 to 0.15 ). These values are lower than the distance between present-day Europeans and East Asians (F st =0.11) (17). Despite this the two ancient genomes belonging to the Siberian Okunevo culture (RISE515 and RISE516) were somewhat of an outlier, exhibiting modest differentiation relative to the EUR sample when compared with the other genomes in the sample (average F st =0.074 vs. 0.016 for the remainder of the sample). Their removal reduced the genetic differentiation between the two samples, yielding 99 ancient genomes, sourced from sites located in present-day Armenia (8.08%), Czech Republic (6.06%), Denmark (6.06%), Estonia (1.01%), Germany (10.1%), Hungary (10.1%), Italy (3.03%), Kazakhstan (1.01%), Lithuania (1.01%), Montenegro (2.02%), Poland (7.07%), Russia (36.36%) and Sweden (8.08%).But this part is just weird.
Changes in allele frequencies can also occur via population expansion and replacement, perhaps driven in part by the relative advantage in conflict conferred upon populations by GCA. Consistent with this, as a possible result of the Neolithic revolution and during the Bronze Age in Europe, three Y-chromosomal haplogroups (R1a, R1b, I1), which are associated with farming or pastoralist cultures, came to mostly replace the formerly dominant hunter-gatherer lineages (associated predominantly with haplogroups G2a and I2) (32). Ancient farming societies in particular are associated with higher social complexity and the use of more complex tools (11); furthermore the contemporary distribution of these three haplogroups is positively associated with the variation in cognitive ability among contemporary European nations (32). The major population movements occurred in the period between 3.5 and 7.3 kybp, however, as noted in (17), westward migration of populations associated with haplogroup R1a continued from the Pontic-Steppe region between 5 and 1.4 kybp.Needless to say, an intervention was begging, so I left the following comment at bioRxiv under the preprint. It'll be interesting to see how the authors incorporate this information into their model.
That's not correct. G2a is the main early farmer lineage of Neolithic Western, Central and Southern Europe, and it arrived in Europe with early Neolithic farmers from Anatolia. I2 is the main hunter-gatherer lineage of Mesolithic Western, Central and Southern Europe. R1a and R1b appear to be the main hunter-gatherer lineages of Mesolithic and Neolithic Eastern Europe (keep in mind that the Neolithic in much of Eastern Europe was defined by the presence of pottery, not necessarily any type of farming). At some point hunter-gatherers native to Western, Central and Southern Europe carrying I2 were acculturated into farming societies, and so I2 rose in frequency in farmer populations at the expense of G2a. Then, during the Eneolithic/Copper Age, foragers on the Eastern European steppe carrying R1a and R1b mixed with pastoralists from the fringes of the steppe, like the North Caucasus, and became steppe pastoralists. These steppe pastoralists with Eastern European forager-derived R1a and R1b then expanded rapidly and moved en masse into the rest of Europe, largely replacing the farmer G2a and I2 lineages there. It's still a mystery how I1 fits into the picture. But it's probably just a North European forager-derived lineage that got caught up somehow in the expansions of the steppe pastoralists or their descendants.Citation... Woodley et al., Holocene selection for variants associated with cognitive ability: Comparing ancient and modern genomes, bioRxiv, February 21, 2017, doi: https://doi.org/10.1101/109678