The set of anatomically modern humans who left Africa and interbred with Neanderthals ~50,000 years ago left a genomic legacy: 1.5-4% of the DNA within today's Eurasians comes from Neanderthals [1,2]. Simonti and colleagues recently aimed to study the extent to which this Neanderthal heritage impacts risk of disease. To do so, they identified Neanderthal alleles in the genotyping data available within the Electronic Medical Records and Genomics (eMERGE) cohort, which contains both genotyping data and phenotype data for health outcomes from electronic medical records. They then analyzed the set of Neanderthal-introgressed alleles in a genome-phenotype association of 28,416 adults of European ancestry. Surprisingly, they found an enrichment of circadian genes among the set of alleles that explain an observed risk for depression . Depression is a condition that's been linked to light , and the persistence of Neanderthal-circadian-related alleles may reflect a tolerance to light exposure at higher latitudes. So what does this imply?
Given the widespread use of artificial lighting at night and the lack of strong exposure to light during the day that accompanies indoor work activities, exposure to light today differs substantially than it did for Neanderthals. This statement is equally true for those without Neanderthal ancestry. What we don't know is the extent to which circadian disruption from chronically aberrant exposure to light at the wrong times varies by variation in circadian genes, which may have been selected due to the influence of light at different latitudes.
I'm a Public Health Genetics PhD student at the University of Washington and a molecular epidemiology research fellow at the Fred Hutchinson Cancer Research Center. I post (mostly) about topics in epidemiology and genetics.