Is that true? And if so, where did those people come from? Sorry for the broad question but I'm having a hard time continuing this book without understanding this issue.
You may be thinking of Tom Dillehay's archaeological work at the Monte Verde site in Chile. It has been dated to at least 18,000 years or so ago with some suggestions that it could date as far back as around 30,000 years or so ago. The consensus at this point is that the people there represented the southward expansion of humans who crossed over the Bering land bridge.