The book describes the revolution currently taking place in archeology thanks to the technology of ancient DNA sampling. It reveals a rich pattern of human dispersal and mixing over the past 100,000 years. In the very distant past it shows that there was interbreeding with Neaderthals and Denisovans, making us non-Africans something of a hybrid. There’s even some suggestion that Eurasian features like lighter skin might be inherited from them. In the more recent past it clears up some archeological disputes about whether cultural change in the archeological record is due to copying or population movement. It seems it’s almost always the latter. Also differences in Y-chromosome and mitochondrial DNA ancestry shows that in many cases males from the incoming population mated with females from the existing one. This is especially true of the Yamnaya people of the central European steppe who spread into northern Europe and South Asia around 4,000 years ago bringing indo-European languages, horses, and the wheel. It really is incredible to think of all the people struggling to survive over millennium, moving from place to place and fighting each other for dominance. How we are all the descents of a long line of survivors. Reich writes very well. It’s a very practical book that lays out the discoveries in a matter-of-fact style. He’s obviously very touchy about any association with theories of racial superiority, and explains at length how his discoveries do not support some of the more lurid online claims made about them. I thought his appeal to liberal ideas about individual equality regardless of one’s genetic inheritance was very good, and an excellent antidote to both right-wing racial supremacists and woke identity politics. This is a very exciting field. Reich describes how we might soon see a complete historical atlas of human movement and evolution. I expect he’ll have to write another book in a few years time with the updates.