
A new paper strongly bolsters that conclusion.3 In "Genomics of adaptive evolution in the woolly mammoth" a large international team of researchers sequenced genomes from 23 woolly mammoth remains and examined genes for proteins that had the most "fixed" amino acid mutations (that is, mutations that occurred in all of the genomes that were sequenced, and so very probably were widely present in the mammoth population). They evaluated the mutations by something called an "aggregated SIFT score." SIFT stands for "Sorting Intolerant From Tolerant."4 In the paper, the higher the aggregated SIFT score, the more likely the amino acid mutations were to not be tolerated by the protein's structure — that is, to disrupt the protein's activity. Of the 31 most highly mutated genes (Table S5), the great majority had high aggregated SIFT scores for the number of mutations they carried, and 21 of the genes each contained one or more "high impact" mutations (very likely to disrupt structure). Only four genes had low aggregated SIFT scores. (Interestingly, one of those is the BRCA2 gene, whose mutation in humans can lead to breast cancer.)












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