Abstract
Mutations occur at vastly different rates across the genome, and between populations. Here, we measure variation in the mutational spectrum in a sample of human genomes representing all major world populations. We find at least two distinct signatures of variation. One, private to certain Native American populations, is novel and is concentrated at CpG sites. The other is consistent with a previously reported signature characterized by TCC>TTC mutations in Europeans and other West Eurasians. We describe the geographic extent of this signature and show that it is detectable in the genomes of ancient, but not archaic humans. We hypothesize that these two signatures are driven by independent processes and both result from differences in either the rate, or repair efficiency, of damage due to deamination of methylated bases – respectively guanine and cytosine for the two processes. Variation in these processes could be due to environmental, genetic, or life-history variation between populations, and dramatically affects the spectrum of rare variation in different populations.
