"Migration is a widespread human activity dating back to the origin of our species. Advances in genetic sequencing have greatly increased our ability to track prehistoric and historic population movements and allowed migration to be described both as a biological and socioeconomic process....

This paper examines a famous puzzle in social science. Why do some nations report such high happiness? Denmark, for instance, regularly tops the league table of rich nations' well-being; Great Britain and the US enter further down; France and Italy do relatively poorly. Yet the explanation for...