The ancestors of today's Indigenous people arrived in the Americas during the coldest part of the last ice age, study suggests

Archaeologists have been arguing for more than a century about whether people first entered the American continents before, during or after the coldest peak of the last ice age, called the Last Glacial Maximum (LGM). Now, a new study of the available genetic evidence suggests the group that gave rise to today's Indigenous people migrated to the Americas no earlier than 21,000 years ago.

"The evidence points to the arrival of humans ancestral to contemporary Indigenous peoples likely near the end of the Last Glacial Maximum, but earlier migrations may also have occurred," study co-authors Bethany Potter , an archaeologist at the Kansas Geological Survey, and Savannah Hay , a biological anthropologist at the University of Kansas, told Live Science in an email.

In a study published online Sept. 23 in the journal Current Opinion in Genetics & Development , the researchers used genetic evidence to investigate the three main archaeological models for Native American origins: an entry into the Americas before the LGM more than 25,000 years ago, entry during the LGM some time between 25,000 and 14,000 years ago, and entry after the LGM more recently than 14,000 years ago, sometimes called the Clovis First theory .

"The reason this topic is so contentious among anthropologists is because not all archaeologists agree about which of the earliest sites are legitimate, and that influences which model they think is most accurate," Potter and Hay said. "We know that humans were definitely in the Americas by about 13,500 years ago. We still don't know if they arrived earlier than that and, if so, how much earlier."

Genetic evidence of the first people in the Americas is scarce. The first whole genome from an ancient Indigenous person, who lived around 4,000 years ago in Greenland, was sequenced in 2010 . Since then, the researchers wrote in the study, scientists have published around 250 whole genomes, along with genome-wide data from around 1,200 ancient Indigenous people.

These DNA studies have revealed key information about the first people in the Americas. During the LGM, around 25,000 years ago, a group of people living somewhere near Siberia or Beringia, which included the land bridge connecting Asia to Alaska, split into different groups ‪—‬ ancient Native Americans, ancient Beringians and one or more "ghost" lineages ‪—‬ and moved quickly along the Pacific coast, possibly splitting again around 16,000 years ago into Northern Native Americans and Southern Native Americans.

Although the current genetic data lines up with archaeological evidence of people entering the American continents at least 14,000 years ago and perhaps as far back as 21,000 years ago, more DNA evidence is needed to fully understand how and when the first Indigenous people arrived from Siberia.

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