"Three major movements of people, it now seems clear, shaped the course of European prehistory. Immigrants brought art and music, farming and cities, domesticated horses and the wheel. They introduced the Indo-European languages spoken across much of the continent today. They may have even brought the plague. The last major contributors to western and central Europe’s genetic makeup—the last of the first Europeans, so to speak—arrived from the Russian steppe as Stonehenge was being built, nearly 5,000 years ago. They finished the job."