Archaeologists have found evidence that disproves the idea that the Clovis people were the first to spread across the Americas via a corridor between the ice sheets of modern Canada.

For a long time it was thought that humans made it from Siberia to Alaska via the Bering land bridge, before moving down the corridor. Later it was fund that there were other people in the Americas before the Clovis, and recent evidence suggests that the Clovis did not even arrive in the Americas via the corridor writes Eva Botkin-Kowacki for The Christian Science Monitor.

Clovis America
Image source: Wikimedia Commons

Clovis-first theory disproved

The research was published Wednesday in the journal Nature, and shows that the ice-free corridor across Canada would not have been suitable for human passage until 12,600 years ago. However the Clovis were living to the south by 13,500 years ago.

The basic story remains the same. As sea levels lowered during the Ice Age, making a land bridge out of the Bering Strait, ancient peoples moved from Siberia to what is now Alaska. They were prevented from moving any further by the ice sheets, and stayed put for thousands of years.

By 16,000 years ago they had worked out how to get around the ice sheets, with scientists debating how they did it. One theory is that they moved down the Pacific coast by boat, or via an ice-free coastal walkway.

Did Clovis use ice-free corridor?

Scientists have since found evidence of human habitation as far south as Chile from long before the Clovis culture appeared. This means the Clovis model first is dead.

However it is still not known whether the Clovis descended from those that came down the Pacific coast. This would meant that they either “were here already and didn’t need a corridor, or whether they represent a separate and later migration and – if so – whether they could have come down the ice free corridor,” said study co-author David J. Meltzer, a paleoanthropologist and archaeologist at Southern Methodist University.

The study shows that they did not go down the corridor, but it’s not just a question of timing.

Migrating humans rely on environment to survive

Even though the corridor became ice free earlier, it does not mean that people could have used it to migrate. In fact the Earth would have taken a long time to recover from the ravages of the Ice Age, and there wouldn’t have been enough food sources or wood to sustain human life.

“It’s 1,500 kilometres. You can’t pack a lunch and do it in a day,” said Meltzer. The researchers then looked at when plants and animals were able to survive in the corridor, using radiocarbon dating to see when life came back to the area.

Their results show that the ice corridor only became biologically viable for humans after the Clovis people first appeared south of the ice sheet. Another study published in the Proceedings of the National Academy of Sciences in June described how bison populations from north and south of the ice sheets didn’t mix until around 13,000 years ago.

“Given that their approach is completely independent from that used in our bison study, I find it encouraging that there is only an ~400 year discrepancy between the two estimates,” said Peter D. Heintzman of the University of California, Santa Cruz, the lead author of the bison study.

Heintzmann points out that “both papers are in agreement” on the importance of the ice-free corridor to migrating humans. “They both suggest that the corridor opened too late for it to be the route for initial colonization of the Americas south of the ice.”

Meltzer says that this means the Clovis people could not have moved down the corridor. “I think we both also agree that the first hard [archaeological] evidence in the corridor when it finally opens is post-Clovis in age, and likely from people moving north and not south.”