Lactase is an enzyme in humans which breaks down lactose, one of the sugars in milk - VCE - SSCE Biology - Question 17 - 2007 - Paper 1

Research indicates that individuals with the adult lactase-producing allele benefit from an enhanced ability to digest lactose, particularly in cultures that have historically relied on dairy as a major part of their diet. This adaptation likely provided a nutritional advantage, allowing these individuals to access essential nutrients from milk, which may explain why this allele became prevalent in European populations over time. Additionally, the absence of the adult lactase allele in Neolithic Europeans suggests that the dietary reliance on dairy products may not have been as critical during that period.