Recent human evolution: European height

These results were announced last year at a conference talk, now hot off the press at Nature Genetics. As stated in the abstract below, the results are important because they show that selection pressure can work on existing variation in polygenic quantitative traits such as height (no new mutations required! See also here). Group differences in the phenotype are (according to the analysis) not due to drift or founder effects -- it's selection at work. Of course, this has been demonstrated many times in the lab, but certain people refuse to believe the results could apply to Homo sapiens, over timescales of order 10ky.

Nature Genetics: Evidence of widespread selection on standing variation in Europe at height-associated SNPs 

Strong signatures of positive selection at newly arising genetic variants are well documented in humans1, 2, 3, 4, 5, 6, 7, 8, but this form of selection may not be widespread in recent human evolution9. Because many human traits are highly polygenic and partly determined by common, ancient genetic variation, an alternative model for rapid genetic adaptation has been proposed: weak selection acting on many pre-existing (standing) genetic variants, or polygenic adaptation10, 11, 12. By studying height, a classic polygenic trait, we demonstrate the first human signature of widespread selection on standing variation. We show that frequencies of alleles associated with increased height, both at known loci and genome wide, are systematically elevated in Northern Europeans compared with Southern Europeans (P < 4.3 × 10−4). This pattern mirrors intra-European height differences and is not confounded by ancestry or other ascertainment biases. The systematic frequency differences are consistent with the presence of widespread weak selection (selection coefficients ~10−3–10−5 per allele) rather than genetic drift alone (P < 10−15).

Here's part of what I wrote a year ago about this result:

3. If the results on selection hold up this will be clear evidence for differential selection between groups of a quantitative trait (as opposed to lactose or altitude tolerance, which are controlled by small sets of loci). We may soon be able to conclude that there has been enough evolutionary time for selection to work within European populations on a trait that is controlled by hundreds (probably thousands) of loci.

Current best guess for number of height loci is of order 10k.