Problem
• Do the data on lactase persistence support the idea that humans are evolving? Use data to support your answer. The data on lactase persistence provides strong support that humans are evolving. In the last 10,000 years, different mutations that enable human adults to digest milk became prevalent in some human populations. In cultures that practiced dairying (in other words, consumed milk or milk products), the ability to digest milk as adults could provide a survival and reproductive advantage. In these populations, the lactase-persistence allele would have increased in frequency over time. This change in allele frequency is evidence for evolution.
• Does lactase persistence provide an example of a selective sweep? Use data to support your answer. Individuals of African and European ancestry who are lactase persistent have areas of reduced genetic diversity (homozygosity) around the lactase gene, providing evidence of a selective sweep for the mutation that gave rise to lactase persistence in these populations.