ABSTRACT
In this chapter, the authors consider the people current understanding of the evolutionary past of humans. They also show how it helps the reader to understand aspects of their biology that would otherwise be puzzling or even paradoxical. Some fossils and non-fossilized bones or teeth contain traces of DNA, and analysis of these is currently transforming our understanding of the human past: a technological revolution that has been compared in its impact to the introduction of radiocarbon dating in the mid-twentieth century. The authors focus on two well-characterized examples where both the genetic and functional evidence for a selective sweep are particularly clear-the lactase gene in populations that drink fresh milk and the EPAS1 gene in high-altitude Himalayan populations living in conditions of permanent hypoxia. Several different variants in the lactase enhancer are known to cause lactase persistence, but each one is present only in a restricted number of populations.
