Mooney helps readers explore the discoveries scientists have made about the human genome. These discoveries help us better understand and treat certain diseases, trace our human ancestry and migration, and compare our species to others. She also explores some of the ethical, legal, and social issues that arise from advances in genomic science.

20,000 years ago, people crossed a great land bridge from Siberia into Western Alaska and then dispersed southward into what is now called the Americas. Until we venture out to other worlds, this remains the last time our species has populated an entirely new place, and this event has been a subject of deep fascination and controversy. No written records--and scant archaeological evidence--exist to tell us what happened or how it took place. Many...