Genetic review pushes back arrival date for first Americans

People reached the Americas earlier than long believed, with their ancestors splitting into northern and southern branches by about 15,500 years ago, a new review of genetic evidence suggests, ERR reports.

Anthropologists at the University of Kansas compared genetic data with archaeological findings. The information came from earlier studies covering the remains of 1,200 ancient Americans.

For decades, researchers generally believed the first settlers entered North America about 13,500 years ago through an ice-free corridor created as glaciers melted. The review indicates that the ancestors of Indigenous Americans had already divided into northern and southern branches thousands of years earlier, probably in places south of the continental ice sheets.

The settlement of South America also appears to have unfolded in several stages. One group arrived before 9,000 years ago, followed later by a large-scale population replacement linked to another migration. A further migration about 2,500 years ago brought genes associated with present-day Central Americans to the Caribbean islands and South America.

The genetic evidence raises questions about archaeological traces of human presence dating back more than 20,000 years, including a 23,000-year-old site at White Sands. Researchers say known ancient genetic lineages began branching more extensively only about 21,000 years ago.

If people lived on the continent before the last ice age, they may have belonged to a lineage that left no lasting descendants, or whose genetic material has not yet been found. Researchers say the earliest Americans are difficult to study because the groups were small and left few physical traces.

The review was published in Current Opinion in Genetics and Development.