“Cultural change is actually happening because people are moving around and not just through the spread of ideas,”says Eske Willerslev of the Natural History Museum of Denmark
Nebra Sky Disc, Early Bronze Age ca. 3600 BP, bronze and gold sheet. The earliest astronomically correct representation of the night sky. Burgenlandkreis district, Saxony-Anhalt.
Analysis of the genomes of 101 individuals who lived in Europe and Central Asia during the Bronze Age—between 5,000 and 3,000 years ago—suggests that the economic and social changes that occurred during this period were due to massive migrations.
Reconstruction of a Yamnaya skull. A typical Yamnaya individual from the Caspian steppe in Russia ca. 5,000-4,800 BP. Yamnaya people were tall and were buried in deep pits covered by a small barrow. Ten thousands were built during this period in the Pontic-Caspian steppe, but also in temperate Europe thousands were built as a result of the migrations. (Reconstruction: Alexey Nechvaloda)
Genetically speaking, ancient Europeans from the time after Bronze Age migrations are much more similar to modern Europeans than those prior to it.
The migration of the Yamnaya Culture into northern Europe. (Modified map after an original by Richard Potter).
Stannous Flouride's Book of Truthiness 