It was previously thought that humans settled in the Americas fairly late, long before the settlement of other continents was complete. Newly discovered footprints dating from 40,000 years ago may unravel this belief, as well as our picture of early man. The case for a late arrival of humans into the Americas is based on both archaeological evidence, as well as on genetic evidence drawn from modern populations.
However, both lines of evidence do not exclude the possibility of earlier habitation, provided that it was limited enough in scope. Perhaps early humans did arrive to the New World but did not manage to successfully colonize it and create a lasting presence. If that is the case, then we would not expect to find traces of the genes of these early colonists among living Native Americans, and the archaeological evidence would be meagre, or absent.
The new discovery does not of course prove that man arrived to the New World at an early age, but hopefully it may trigger more research into the earlier geological time periods, which were hitherto considered to be archaeologically barren.