Keep in mind that the Joman peoples of Japan were already exploring the Pacific down to South America over 14,000 years ago ... so anything is possible. Trying to pin down in more recent times who moved where when over this time scale is simpily research in search of grant money.
Yup.
Here's the proof:
"The oldest human remains found in the Americas were recently "discovered" in the storeroom of Mexico's National Museum of Anthropology. Found in central Mexico in 1959, the five skulls were radiocarbon dated by a team of researchers from the United Kingdom and Mexico and found to be 13,000 years old.
Of additional significance is the shape of the skulls, which are described as long and narrow, very unlike those of modern Native Americans.