About an hour southwest of Pittsburgh, Pennsylvania, a shallow, 10-metre-wide creek meanders through a valley thick with the vegetation of the eastern deciduous forest.
Over the millennia, Cross Creek has wandered back and forth across the valley, gradually widening and deepening it.
On one south-facing cliff face it carved out a hollow in the underlying, soft brown sandstone.
As the stream ate its way into the cliff, it formed a wide, sheltered bench. The gradual erosion of the valley left this rock shelter high and dry some 25 metres above the present creek level.
The prevailing east to west winds cleared smoke and insects from the site making it an ideal camping spot with plenty of water and out of the elements under the shelter of the overhanging cliff.
James Adovasio first saw the site in 1973 as a young archeologist charged by the University of Pittsburgh to open and run an archeological field school.
He also saw the Meadowcroft Rockshelter as a prime place to put up camp for a while. Just inside the drip line of the overhanging rock a firepot showed recent usage. Pull-tab beer cans lie inside the circle of stones.
In the first summer’s dig, Adovasio and his students found an earlier campfire layer directly underneath littered with steel beer cans.
Deeeper yet, they found old-style glass beer bottles and then, below them, colonial-era gin bottles predominated some of which had been reworked into tools by the last woodland Indians inhabiting the region.
The deeper they dug the further they reached back into the history of the human settlement of North America.
They reached so far back that they found themselves challenging the then-dominant Clovis theory that hunters of mega fauna, like the mammoth, were the first people on this continent.
Professor Adovasio knew that the information carefully gleaned from the Meadowcroft Rockshelter, a trowel at a time, would provoke a challenge from defenders of the Clovis-first theory.
But what could Adovasio do but lay out the data from his dig?
The picture became clear: By 16,000 years ago, the glaciers had retreated some 300 kilometres north to about the line of the present Lake Erie.
Vegetation had aggressively reclaimed the protected valleys, like this one, which I visited last weekend.
The narrow valley also provided easy egress from the then tundra-like Allegheny Plateau down to the Ohio River.
About 12.2 kilometres from where Cross Creek joins the Ohio River, the Meadowcroft Rockshelter would have provided a perfect haven for the first aboriginal pioneers on their seasonal round.
More than a million seeds and other flora remains have been excavated from the rock shelter along with 1.5 million faunal clues.
These provide the evidence the site was mainly used in the fall by its visitors, including the first pioneers who frequented it 16,000 years ago.
Overwhelming evidence now backed up by similar Clovis-shattering discoveries such as at Monte Verde in Chile, Cactus Hill, Virginia, and a host of other emerging sites have laid the foundation for a new paradigm.
This sees many migratory pulses coming from Asia into the Americas starting 20,000 years ago, or even earlier.
Varied lithic technologies in the archeological record, mitochondrial DNA markers and linguistic analysis of current First Nations citizens are among the information sources buttressing the emerging theory based in part on the findings from the Meadowcroft rock shelter.
Still Jim Adovasio told me last Saturday that some Clovis firsters will go to their graves defending their theory.
How long does it take to change a paradigm? How overwhelming must the evidence be?
A mounting chorus of voices says that voluminous evidence clearly points to the fact that our current global economic system just doesn’t work.
How long will it take to shake ourselves clear of that inequality and poverty-producing paradigm?
By the way, Adovasio said he would be happy to consider an invitation to come lecture in the Yukon. Maybe the Yukon Science Institute should consider inviting him for their fall speaker series?