Book Upends Theory About First Americans' Arrival Visitors may have gotten here thousands of years earlier than thought By Matt Cantor, Newser User Posted Mar 1, 2012 2:23 PM CST 15 comments Comments The first humans may have arrived here 20,000 years ago. (Shutterstock) (Newser) – Forget what you learned in school about the first Americans: A new theory is turning archeological assumptions upside down. A pair of experts on ancient history assert that the first Europeans arrived in the Mid-Atlantic region 20,000 years ago, during the Stone Age—rejecting the standard theory that North America was unpopulated until Siberians arrived 15,000 years ago. While the theory was considered laughable a few years back, Dennis Stanford and Bruce Bradley's new book is winning converts, the Washington Post reports. In 1999, some suggested that the so-called "Solutrean hypothesis" could end Stanford's career. "I had been very dubious," notes a Texas State archeologist. But after reading Across Atlantic Ice, "I drank the Solutrean Kool-Aid." The theory rests on the discovery of ancient tools in the Mid-Atlantic region, including blades that match Stone Age ones from Spain and France, Stanford says. But there's still plenty of doubt: For instance, the dates were based on tests of the soil around the tools, not the tools themselves. Click through for more on the Stone-Age debate.