"Since the appearance of modern humans in Africa around 200,000 years ago, we have migrated around the globe and accumulated genetic variations that affect various traits, including our appearance, skin color, food tolerance, and susceptibility to different diseases. Large-scale DNA sequencing is now allowing us to map the patterns of human genetic variation more accurately than ever before, trace our ancestries, and develop personalized therapies for particular diseases. It is also reinforcing the idea that human populations are far from homogeneous, are highly intermixed, and do not fall into distinct races or castes that can be defined genetically." -- From the publisher's description