There are two main hypotheses regarding the lactose persistence mutation. Firstly, the “culture-historical hypothesis” states that alleles for lactose persistence were low until humans domesticated dairy animals in the early Neolithic and then rose sharply due to the selective advantage it conferred and natural selection. The “reverse cause hypothesis” states that dairy animals were utilized in populations with preadaptive high lactose persistence. Researchers have discovered that lactase persistence likely arouse through convergent adaptation. Scientists studied 470 Tanzanians, Kenyans and Sudanese in a genotype-phenotype association study which focused on three SNPs associated with lactase persistence “These SNPs originated on different haplotype backgrounds from the European SNP and from each other...These data provide a marked example of convergent evolution due to strong selective pressure resulting from shared cultural traits—animal domestication and adult milk consumption. (Sarah Tishkoff et al., 2007)” This case of convergent evolution with African and European populations is strong evidence that human populations are evolving. Mutations likely arose independently in these two populations that allowed for lactase persistence. Since the mutations conferred a selective advantage, these alleles were favored by natural selection and increased in frequency.
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