How did the artifacts found at meadowcroft rock shelter change many archaeologists theories?

The peopling of America has long been a very controversial subject with adherents of one theory or another fiercely defending their positions. It was long held that the Clovis people were the first humans in North America and the Clovis first crowd still holds that view. But finds Ar Meadow croft and other places have all but debunked the Clovis first position. Artifacts at Meadow croft are dated to between 16,000 and 19,000 years. If the 19,000 dating is correct then Meadow croft would be the oldest known site of human habitation in the Western Hemisphere.