[Luis Gonzalez]

"My original position was that Mexico was settled in the dim past by South Americans."

There was no "South" America in the dim past.

North, Central, and South America are post-Columbian divisions.

[William Terrell]

There was a land mass where what is now called "South America" in the past. I think we can be reasonably certain that the area now known as Mexico was settled after the continental drift.