Evolution of lactase persistence: an example of human niche construction

TLDR

Niche construction describes how organisms modify their environment, and lactase persistence—continued lactase production into adulthood—is a prominent human example driven by the -13910*T mutation in Europeans and multiple mutations elsewhere, with allele ages aligning with the advent of animal domestication and dairying practices. The authors aim to update the geographic distribution of the -13910*T allele, synthesize global genetic diversity of lactase persistence, and evaluate archaeological evidence through simulation studies to better understand its evolution. They compile new allele frequency data, review archaeological records, and conduct three simulation models that integrate genetic and cultural dynamics to trace lactase persistence spread in Europe. These integrated analyses reveal how genetic and archaeological evidence together illuminate the origins and dissemination of lactase persistence.

Abstract

Niche construction is the process by which organisms construct important components of their local environment in ways that introduce novel selection pressures. Lactase persistence is one of the clearest examples of niche construction in humans. Lactase is the enzyme responsible for the digestion of the milk sugar lactose and its production decreases after the weaning phase in most mammals, including most humans. Some humans, however, continue to produce lactase throughout adulthood, a trait known as lactase persistence. In European populations, a single mutation (-13910*T) explains the distribution of the phenotype, whereas several mutations are associated with it in Africa and the Middle East. Current estimates for the age of lactase persistence-associated alleles bracket those for the origins of animal domestication and the culturally transmitted practice of dairying. We report new data on the distribution of -13910*T and summarize genetic studies on the diversity of lactase persistence worldwide. We review relevant archaeological data and describe three simulation studies that have shed light on the evolution of this trait in Europe. These studies illustrate how genetic and archaeological information can be integrated to bring new insights to the origins and spread of lactase persistence. Finally, we discuss possible improvements to these models.