Infographic: Mixed Evidence on Human Occupation of the Americas – The Scientist

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Emma is a Florida-based freelance journalist and regular contributor for The Scientist.
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For decades, scientists subscribed to the Clovis-first model of the peopling of the Americas, the idea that the earliest humans on the landmass had crossed the Bering Land Bridge after the Last Glacial Maximum when glaciers began to recede, about 13,000 years ago. These people spread widely throughout North and South America, as evidenced by the leaf-shaped spearheads they left behind. Some discoveries have begun to poke holes in the model, however. The Clovis people were in the Americas 13,000 years ago and did spread widely, but it’s becoming more and more clear that they weren’t the first humans to inhabit the New World.
Genetic sequencing of H. pylori bacteria from the stomachs of modern humans suggested that an ancient population of people survived in the area during the Last Glacial Maximum, when the land was covered in ice. 
Comparing DNA from the bones of a girl with sequences of DNA from other ancient populations and with genomes of modern Native Americans showed that she was part of a previously unknown group that separated from modern Native Americans about 20,000 years ago, suggesting that multiple groups migrated into and through North America. 
Fifteen ancient genomes spread across the Americas revealed two distinct migrations from North to South America, highlighting the complexity of early human migrations and suggesting that early people had wide access to the continents that allowed them to rapidly spread throughout, despite obstacles such as glaciers.
Footprints found in White Sands National Park revealed human activity in the area for thousands of years during the Last Glacial Maximum.
Stone artifacts, animal remains, and burn sites uncovered in 1988, with new samples revealed and analyzed in 2015, were the first conclusive evidence that humans were in the Americas before 13,000 years ago. 
For much of the last ice age, massive glaciers covered the northern part of the Americas. After the last glacial maximum, that ice started to melt, and by 13,000 years ago, an ice-free pathway opened through modern-day Canada that scientists know the Clovis people to have traveled. However, recent archeological and genetic evidence suggests that some groups of people migrated to the Americas before the last glacial maximum, when there was no ice-free corridor, suggesting that they may have traveled along the western coastline. If so, many of the artifacts and remains they left behind may be under water.
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This article was featured in May 2022, Issue 1 of the digest
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Mounting evidence suggests people reached the new world thousands of years earlier than previously thought
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