How genes have illuminated the history of early Americans and Latino Americans.

The American continent currently accounts for ∼15% of the world population. Although first settled thousands of years ago and fitting its label as "the New World," the European colonial expansion initiated in the late 15th century resulted in people from virtually every corner of the globe subsequently settling in the Americas. The arrival of large numbers of immigrants led to a dramatic decline of the Native American population and extensive population mixing. A salient feature of the current human population of the Americas is, thus, its great diversity. The genetic variation of the Native peoples that recent immigrants encountered had been shaped by demographic events acting since the initial peopling of the continent. Similarly, but on a compressed timescale, the colonial history of the Americas has had a major impact on the genetic makeup of the current population of the continent. A range of genetic analyses has been used to study both the ancient settlement of the continent and more recent history of population mixing. Here, I show how these two strands of research overlap and make use of results from other scientific disciplines to produce a fuller picture of the settlement of the continent at different time periods. The biological diversity of the Americas also provides prominent examples of the complex interaction between biological and social factors in constructing human identities and of the difficulties in defining human populations.