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.

A Polynesian Interlude
The use of boats had always been rejected by the Bering Strait advocates, because it opened up other possible routes of migration, such as Europe or Polynesia. Thus they had dismissed any contacts between Polynesians and American Indians (and many continue to dismiss evidence of prehistoric contacts), because it would undercut the contention that "primitive people" could not cross the oceans, and that walking across the Bering Strait was the only possible way that Paleoindians could have come to the Americas.

But the presumption that primitive people cannot sail the ocean is a belief born out of the social evolutionary theories of Herbert Spencer and Lewis Henry Morgan–that societies inexorably evolve to greater complexity and skill. Since the Europeans were unable to cross the oceans until the 16th-century, no one else should have been able to do so earlier.

Yet the evidence for pre-Columbian contact between Polynesians and American Indians has always been strong. Before the Bering Strait Theory assumed its dogmatic status, many scientists believed it and few rejected it out of hand. As early as 1837, scientists such as John Dunmore Lang, a prominent Presbyterian minister and Australian politician, proposed Polynesian voyages to America. In his book, Origins and Migrations of the Polynesian Nation, Lang dismissed the Asian-American connection, stating that "there is no evidence, and not the slightest probability, of any emigration having ever taken place from Asia to America by the Behring's [sic] Straits."

Ever since the first proposer of this particular route for the discovery and settlement of America announced his great idea to the world, the learned of all nations, including such names as Humboldt and Dr. Robertson, have caught and adopted that idea and followed in his wake–as blindly, indeed, and as unintelligently as a flock of sheep follows its leader.

Lang, who traveled throughout the Pacific and into the Americas, argued, in a large part through linguistic evidence, that the Polynesians originated in Malaysia and spread across the ocean in a pattern largely confirmed 150 years later by genetic evidence.

Many of Lang's ideas were fanciful, but no more so than any one else's at the time. He believed the Polynesians landed near Copiapo in Chile in some distant past and from there colonized the Americas. The historian George Bancroft (whose dubious accomplishments include instigating the Mexican War as acting Secretary of War under President James Polk), wrote about Lang's theory in 1841 in his influential book, History of the Colonization of the United States, "It would not be safe to reject the possibility of an early communication between South America and the Polynesia world." The distinguished French naturalist Jean Louis Armand de Quatrefages also considered American voyages likely in his 1866 work, The Polynesians and Their Migrations.

There was little doubt in those days that the Polynesians could have made a trans-Pacific voyage. The early settlement of Hawaii, more than 2,500 miles from the northernmost islands of French Polynesia and over 3,000 miles from Tahiti, required a tremendous feat of sailing and navigation. European explorers often recorded meeting Polynesian sailors in the open ocean, including an encounter in 1615 by the Dutch navigator, Willem Cornelisz Schouten, who came across a party of Polynesians in a double-hulled ship more than 3,000 miles from their home in the Marianas.

Lang noted physical and cultural similarities between the two peoples, many of which today would be seen as the result of simple prejudice, but others, such as similar types of fishhooks, canoes, and harpoons used by Indians in California, Chile, and among the Polynesians, were not to be dismissed lightly.

The most important evidence was biological. As early as 1770, Spanish explorers wrote that maize, manioc, and white potatoes, all indigenous to the Americas, had been grown on Easter Island. Similar varieties of coconuts, bottle gourd (calabash), bananas, and chickens, were all seen as evidence of voyages back and forth. Most significantly, the sweet potato, clearly indigenous to the Americas, was found across Polynesia, including Hawaii and New Zealand. In 1866, in the journal Botany, the German botanist Berthold Carl Seemann wrote that the Polynesian name for sweet potato, "Kumara or umara, of the South-Sea Islanders, is identical with cumar, the Quichua name for sweet potato in the highlands of Ecuador."

As if that evidence was not indisputable enough, in 1841, while digging through an ancient Inca temple in Cuzco, Peru, the director of the National Museum of Lima, Mariano Eduardo de Rivero, and the Swiss explorer, Johann Jakob von Tschudi, discovered a distinctive "green amphibole stone ax," that was soon identified as a Maori patu-pounamu, or jade war club, from New Zealand. But as the Bering Strait Theory became predominant in the late 19th-century, the idea of Polynesian-American contact began to lose favor.

By the early 20th-century, only a few anthropologists, such as Roland Dixon, were willing to accept, and even then only half-heartedly, that trans-Pacific voyages by Polynesians might have occurred. Thor Heyerdahl's highly celebrated voyage from South America to Polynesia in the light raft Kon-Tiki in 1947, along with his equally celebrated but extremely doubtful ideas of Polynesian origins, created a huge scientific backlash that basically killed any lingering discussion of trans-oceanic contact.

But the Polynesians did sail to the Americas. Recent DNA studies of sweet potatoes and chickens now confirm that they were traded before contact with Europeans. A flurry of recent articles, including "The Polynesian Gene Pool: an Early Contribution by Amerindians to Easter Island," published in the Philosophical Transactions of the Royal Society in 2012; a 2013 article from the Proceedings of the National Academy of Sciences, entitled "Identification of Polynesian mtDNA Haplogroups in Remains of Botocudo Amerindians from Brazil;" and a 2010 article in Current Geonomics, "The Origin of Amerindians and the Peopling of the Americas According to HLA Genes: Admixture with Asian and Pacific Peoples" have pretty much settled the debate for everyone except the most dogmatic Bering Strait advocates.

The new version of the Bering Strait Theory, what is now known as the "Coastal Migration," has the first Americans using boats, presumably small primitive craft that then skirted the massive ice-sheets along the coast on their way to Aubrey, Texas. But that assumption completely dismisses the reality of the region of the Bering Strait.

As it is presently, even without being surrounded by the massive ice-sheets that would have reached out well into the open ocean back then, the seas around the Bering Strait are among the most treacherous on the planet. European explorers had, for 200 years after they had already circumnavigated the globe, attempted to reach the area without success, failing time and time again because their ships were not capable of even coming close to it, much less crossing it. Navigating those seas requires tremendous technological skill, every bit as daunting as crossing the open ocean.

One could argue, using the example of European or Polynesian voyages, that it would have been just as easy for Paleoindians to have crossed the Pacific or Atlantic, than to try to sail or paddle the seas around the Bering Strait. The presumption had been that Paleoindians walked across a land bridge into the Americas because they were incapable of doing anything else, but if Paleoindians did indeed use boats 15,000 years ago, then they could have come from anywhere.

Time Waits for No One
Now that it became evident that the land passageway to the Americas was effectively blocked, even during the Clovis period, the Bering Strait Theory should have died a natural death, but being a dogma and not a scientific theory, its advocates would simply not let go. After Aleš Hrdlicka's retirement in 1942 from the National Museum, a number of sites potentially older than Clovis had been excavated, but all had been vigorously challenged by a new generation of archaeologists, and all had been dismissed. The demand for "indisputable proof," whatever that might entail, was simply too great an obstacle to overcome. But one man had figured out the game, and in doing so, brought down the Clovis First version of the Bering Strait Theory.

In 1976, Tom Dillehay, an American anthropologist who at that time was working at the Universidad Austral de Chile, began excavating an ancient site in southern Chile. Quickly recognizing the antiquity of this site, his excavation became arguably the most meticulous ever undertaken. It had to be, for when he first announced his findings in 1988, and claimed that the samples of wood from houses, charcoal from hearths, and other artifacts that he had excavated had been radiocarbon dated to be almost 15,000 years old, it sent a massive shock wave through the archaeological community. It meant that this site in South America was more than 1,000 years older than any accepted site in North America. Dillehay's findings were immediately and bitterly attacked by the Clovis First advocates, but he had expected it, and the detail and quality of his work made his conclusions virtually irrefutable. Despite this, it took almost 10 years for the archaeological community to–extremely grudgingly–accept the Monte Verde site.

The fact that the oldest site in the Americas was located almost 8,000 miles from the presumed gateway did not go unnoticed. One might have assumed that if the Bering Strait Theory were correct, and Paleoindians migrated from Asia, then the sites in South America would be much younger than those in North America, and the further north one excavated, the older the sites would be. But that had never been the case, as the accepted sites in Canada were even younger than those in the U.S. Indeed the archaeological evidence was pointed towards a migration, but a migration the other way.

With Clovis First now dead and with it the Ice-Free Corridor, Coastal Migration was now the only alternative. The new dates from Monte Verde had pushed back human occupation of the Americas to 14,800 years ago, but geologists had already determined that 17,000 years ago the coastal route was completely blocked by ice from Russia all the way to Seattle. The Paleoindians would have had to have sailed a distance of almost 3,000 miles alongside the massive ice sheets without being able to land. Even 16,000 years ago the coastal route would have been largely clogged with ice. Once again the Paleoindians would have had to race, this time in tiny boats through treacherous waters, if they were to reach Monte Verde in time to leave traces of their occupation.

The line was drawn once again by the Bering Strait advocates at 15,000 years ago, and it could not go back much further than that without the collapse of the whole theory. So this meant that according to the newest version of the Bering Strait Theory, the Paleoindians essentially sailed down the coast directly to Monte Verde, Chile, before later deciding to settle in the Americas. But as absurd as that idea was, new evidence was making even that far-fetched concept impossible.

Bering Strait Theory, Pt. 6: DNA, Blood Types and Stereotypes