Abstract The natural cycles of night and day, and their length, remain stable in near-equatorial African regions but they vary with latitude and season in Eurasia. This new environmental factor… Click to show full abstract
Abstract The natural cycles of night and day, and their length, remain stable in near-equatorial African regions but they vary with latitude and season in Eurasia. This new environmental factor might shape the adaptation of circadian rhythms of Eurasians after the out-of-African dispersal of their African ancestors. To identify the genetic-based signatures of this adaptation, geographic variation in allele frequencies of more than 2300 genetic variants was analyzed using data from 5 African and 11 Eurasian populations of the 1000 Genomes Project. The genetic signatures of latitude-dependent polygenic selection were found more frequently within non-coding DNA regions associated with morningness–eveningness in genome-wide association studies (GWASs) than among polymorphisms hinted by GWASs of other traits/diseases and among polymorphisms sampled from pseudogenes and from protein-coding regions in either circadian clock genes or reference genes. Some of such variants were located within the introgressions of the Neanderthal’s genome into the genomes of Eurasians.
               
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