Keep pulling the thread on David Reich.
Genetic data indicates the human genome in Europe and the Middle East reacted more strongly to environmental changes around 5,000 years ago during the Bronze Age than to the initial transition to farming.
In a study of 10 million variable genetic positions, approximately 98% of frequency changes are attributed to factors like genetic drift and migration, while only 2% are due to directional selection.
A recent study by David Reich's lab identified approximately 7,200 positions in the human genome with at least a 50% confidence of being under natural selection, estimating that about 3,600 of these are real signals.
Genetic signals of natural selection are vastly enriched by four to five-fold for immune-related traits.
Natural selection in Europe and the Middle East has accelerated over the last 10,000 years, particularly in the last 5,000 years.
The intensification of selection around immune and metabolic traits has accelerated over the last 5,000 years compared to the previous 5,000 years.
The TIK2 genetic variant, a major risk factor for severe tuberculosis, increased in frequency until about 3,000 years ago and then rapidly decreased, suggesting a reversal in selective pressure.
Analysis of ancient DNA from Europe and the Middle East shows strong natural selection for a combination of genetic variants that predict performance on IQ tests in modern populations.
The strength of natural selection on genetic variants associated with cognitive performance peaked during the Bronze Age, between 5,000 and 2,000 years ago, and shows almost no evidence of selection in the last 2,000 years.
The estimated polygenic score for cognitive performance in European hunter-gatherers is approximately three standard deviations below the modern mean.
There is a five or six standard deviation statistical correlation between the effect size of genetic variants on years of schooling in China and the trajectory of those same variants in Europe over the last 10,000 years.
Over the last 10,000 years in Europe and the Middle East, there has been clear genetic selection for a reduction in traits that increase risk for obesity, higher body mass index, and type 2 diabetes.