Many of our "Native American" Indian tribes were extremely primitive, true stone age peoples. On the other hand, many of the Central and South American "Tribes" had developed rather advanced Megalithic, and Metallurgical technologies and a far more advanced culture.
Think I'd heard that the Aboriginal migration into Australia was something like 50 to 100 thousand years ago? I'll have to recheck sources and get back to you on that, but I truly thought that they'd been there a long time before we got ours!