Chapter 5 discusses hypotheses for the genetic ancestry and migration of Native Americans. The chapter discusses a number of different theories, and the tools developed over time to either validate or reject these theories. The first half of the chapter begins with discussion of the sampling of genetic material. The examination of DNA evidence, which began in the 20th century, uses samples from mitochondrial DNA. The use of samples from mitochondrial DNA helps to clear up misconceptions and mystifications of the origins of Native Americans, which had previously been shrouded in mystery. Remarkably, scientists found that Native Americans share a significant amount of genetic material with certain Siberian ethnic groups.

The latter half of the chapter discusses theories of migration, by which the forerunners of Native Americans arrived to the Americas. The principal subject is that Beringia, a land bridge theorized to exist between modern-day Alaska and Eastern Siberia, used to exist, and allowed for migration from Siberia to the Americas. The theory goes that during an Ice Age, the recession of sea levels allowed for peoples to migrate between the continents for a short amount of time. As with many theories in anthropology and archaeology, these hypotheses seemed outlandish to many when they were initially proposed, but as science and understanding improved, the theory grew to be accepted.