Tests on skulls found in Mexico suggest they are almost 13,000 years old... The human skulls are the oldest tested so far from the continent... They came from a collection of 27 skeletons of early humans kept at the National Museum of Anthropology in Mexico City. These were originally discovered more than 100 years ago in the area surrounding the city The two oldest skulls were "dolichocephalic" - that is, long and narrow-headed. Other, more recent skulls were a different shape - short and broad, like those from native American remains. This suggests that humans dispersed within Mexico in two distinct waves, and that a race of long and narrow-headed humans may have lived in North America prior to the American Indians.

Source: BBC