Lactase persistence as a model of selection dynamics

Lactase persistence (LP) is one of the most well-documented cases of recent human positive selection. This thesis examines how LP evolved in Europe by reviewing archaeological lipid-residue evidence, ancient DNA datasets and population-genetic models. While dairying emerged in the early Neolithic period, genomic data indicate that the intensification of strong selection on the LCT/MCM6 regulatory variant occurred only during the Bronze Age. This suggests that the observed increase in allele frequency cannot be solely attributed to milk consumption. Based on existing deterministic selection models and the likelihood-based framework developed in recent studies, this thesis analyses how constant versus time-varying selection regimes can reproduce the LP allele trajectory. Incorporating ecological proxies linked to nutritional stress and pathogen exposure demonstrates that fluctuating selection more accurately matches the empirical data than constant selective pressure. Overall, this thesis synthesises the current evidence and modelling approaches to clarify the ecological and demographic conditions that shaped the evolution of lactase persistence.