It’s been the biggest shock in archaeology in quite some time.
British and American archaeologists have found solid evidence that human beings — we could call them the forerunners — were in the Americas about 6,000 years before the earliest previously accepted date.
What the archaeologists found, at White Sands in New Mexico, was thousands of actual footprints, which definitely beats some chipped stones that might or might not be ancient spear points.
Moreover, the lead author of the report in the journal Science, Prof. Matthew Bennett of Bournemouth University in England, thinks most of the footprints were those of youths.
“These were America’s first teenagers,” he told The Observer. “And they were hanging out together as they do today. The only thing missing then was a smartphone.”
We have no DNA from the White Sands site, but the people who lived by that ancient lake probably wouldn’t even stand out in a modern street if you gave them clothes and a makeover.
What the forerunners have given us, however, is a couple of challenging mysteries. The smaller one is how they got there.
They presumably started by crossing the now-submerged land bridge between Siberia and Alaska. That was the easy bit. But a solid wall of glaciers more than a kilometre high blocked the land route south through Canada from Alaska 22,000 years ago. How did they get around that?
Maybe they had dugout canoes (though big trees were rare in the Ice Age Arctic), but it would have been a very long way down a rocky, ice-clad coast (2,500 kilometres) with nothing to eat but the fish caught.
By comparison the Clovis people, who we used to think were the first humans in the Americas, had it easy.
By the time they showed up about 13,000 years ago, a north-south corridor had opened up through the ice fields in what is now Alberta. You could walk the whole distance to Clovis, New Mexico, and find food all along the way.
From the arrival of the Clovis people onwards, evidence of human presence in the Americas is widespread and continuous. Further research has found that some similar people may have been in the two continents as long ago as 16,000 years ago.
But the bigger mystery is this: If there were already human beings in New Mexico 22,000 years ago, where did they go for the next 6,000 years? How could there not be other evidence of their presence in other places?
Start with the obvious question. Could that date be wrong?
Probably not. You can’t carbon-date footprints in the mud, but you can date the ditch grass seeds that are trapped in the mud (now turned into rock) in the layers just above and below those footprints. The archaeologists tested the date every way they knew and, every time, the answer came out the same — the footprints are between 23,000 and 21,000 years old.
OK, then. Time to ask the question we’d all rather avoid. Could the forerunners be one or more groups that did an end-run around the glaciers 22,000 years ago, thrived for a little while in the Americas, and then for some reason died out?
No evidence for a human presence over the next 6,000 years strongly suggests that the forerunners just weren’t there any more. No mass extinction of American megafauna (large prey animals) until the Clovis hunters arrive 60 centuries later makes it almost certain.
When human hunter-gatherers first settled a continent or ocean island where the prey animals had not co-evolved with human beings and did not fear them, there was always a mass extinction: Australia 46,000 years ago, the Americas around 10,000 to 12,000 years ago, New Zealand only 700 years ago. If it didn’t happen any earlier in the Americas, then the forerunners were probably long gone.
Or maybe, just maybe, they were still hanging on somewhere in small numbers until the Clovis people arrived, probably with better weapons, and swept them aside. That’s what Dr Andrea Manica, a geneticist at Cambridge University, thinks.
He told the BBC that the genetics “clearly shows a split of Native Americans from Asians approximately 15,000 to 16,000 years ago.”
The forerunners are not represented in that genetic lineage and Manica suggests “the initial colonists of the Americas were replaced when the ice corridor formed and another wave of colonists came in. We have no idea how that happened.”
Yes, we do. We just don’t like to think about it.
The world’s prehistory is filled with stories of more powerful groups driving out or wiping out less powerful groups. Often the men and the boy children would be killed, while the women would be kept, but the forerunners (if they were still around to meet the new bosses) weren’t even that lucky.
Sixty centuries — and nothing to show for it.