The claimed ages for the deepest archaeological strata at Meadowcroft extend to 16,000 or possibly older calibrated years before present — significantly before the Clovis horizon.

The Meadowcroft evidence has been contested for decades.

Critics have raised concerns about possible contamination of the radiocarbon samples by old carbon from coal deposits in the groundwater percolating through the shelter, which could make organic samples appear older than they actually are.

Critics have also noted that the flora and fauna represented in the deepest layers appear more consistent with a warmer climate than would be expected at the claimed ages, when the site should have been at the margin of the ice sheet.

Adovasio and his team have defended the evidence against these criticisms, and the debate continues without clear resolution.