Polygenic evolution towards a morning chronotype in modern humans

Phenotypic trend toward morningness increased drastically during anatomically modern human migration above 20 degrees north, linked to polygenic chronotype signals.

• Why it matters: Chronotype shifts with latitude, but the genetic basis and how it changes during human migration remain unclear.
• What they did: Using associated SNPs from a genome-wide association study, the authors performed a polygenic assessment of chronotype trend across latitudinal migration, and tested two modes of latitudinal selection on morningness alleles.
• The result: Two types of latitudinal selection of morningness alleles contributed to establishing the morning chronotype trend at higher latitudes, and the trend is proposed to be stronger in present-day modern humans above 20 degrees north than in Neanderthals.

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