Bering Strait Theory, Pt. 5: The Theory Comes Crashing Down
In Part 4 of our exclusive series we looked at how the Bering Strait Theory by the 1920s had become a rigid dogma that no scientist who valued their career would dare to challenge.
For most of the 20th century, new discoveries of American Indian origins that cast doubt on the Bering Strait Theory were either dismissed or ignored. But as the technology of science marched on, the cracks grew deeper and deeper.
An unintended consequence of the atmospheric testing of atomic weapons during the Cold War was that by the 1960s it had doubled the amount of radioactive carbon 14 in the environment, and this “bomb pulse” was showing up on the instruments that were used for radiocarbon dating. This led scientists to suspect that the amount of carbon 14 that is found in the environment might not have always been constant, possibly leading to wrong dates.
By the mid-1980s, dendrochronologists, those that study and date tree-rings, had manage to piece together–by matching the tree-rings of long-living species such as the bristlecone pine with those of ancient trees–an unbroken string of tree-rings over 7,000 years old. Since dendochronology can give extremely accurate dates, often to the year, matching the two dating systems found exactly that, that the amount of C14 fluctuated and that many radiocarbon dates had to be adjusted.
For Clovis First advocates, this presented a real problem, for the new calibrated radiocarbon dates pushed back the Clovis culture almost 2,000 years. It meant that the oldest reliably dated Clovis site, in Aubrey, Texas, which was radiocarbon dated at 11,590 years ago, was now approximately 13,490 years old. The Paleoindians would have had to race through the Ice-free Corridor to get to Texas in time.
But the new radiocarbon dates would give even more bad news. Geologists, also recalibrating their radiocarbon data, began to refine their estimates for when the massive ice sheets began to melt, and found them adjusting their dates between 500 and 2,000 years earlier. The Ice-free Corridor was now certainly impassable 13,000 years ago and possibly as late as 12,000 years ago. This meant that there was no way the Paleoindians could have walked over from Asia–or if they had, they would have had to done so 20,000 years earlier, a non-starter for the theory’s advocates. A central thesis of the Bering Strait Theory was now toppled, for if the Clovis culture was indeed the first peoples in the Americas, they had to have come by boat.
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