These variants are inherited just like any other allele. What ancient DNA revealed, especially through large-scale studies in the last few years, is that the lactase-persistence allele was extremely rare for thousands of years, even long after dairy animals were domesticated. By comparing ancient genomes across time, researchers showed that this allele increased dramatically only in the last few millennia, likely because individuals who could digest milk had a survival advantage during times of famine or disease.
Even small differences between ancient and modern DNA reveal how populations changed over time, how isolation, disease, and adaptation shaped who we are today. When we study ancient genomes, we’re not just looking backward. We’re understanding different biological processes (including mutation, selection, and inheritance) that are relevant even now.
