[blam]

"I have always thought that the reason "old sites" were not found it the Northern Hemisphere was that no one looked."

This is exactly what happened at either the Meadowcroft or the Topper site (Can't remember which). The discoverer dug down to the Clovis level then stopped. Only after the discovery of the Monte Verde site did he decide (years later) to go back and dig deeper. Below the Clovis level, guess what, he found even earlier human artifacts.