Michael Waters and colleagues  report on the date of a mastodon kill site from Manis, Washington. At 13,800 years old, it's not the earliest evidence of New World people, nor the only evidence of pre-Clovis hunting. I find it interesting because of the addition of genetics to the mix of evidence. The specimen is verified as a mastodon, and the bone used to kill it was itself made of mastodon bone:
We also obtained high-resolution tandem mass spectrometry (MS/MS)–based protein sequences from the projectile point and rib, and used another mastodon sample as a second reference (tables S3 to S6). The MS/MS spectra from the bone point matched the reconstructed mastodon collagen sequences, with the highest scores being within a reference set of collagen sequences (table S7 and supporting table of bone point marker peptides). These results and controls show that the point was fashioned from mastodon bone.
The conclusion of the paper suggests that the evidence of pre-Clovis megafauna hunting argues against a "blitzkrieg" scenario for megafaunal extinctions. Instead, the authors suggest that the extinction was staged over a period of nearly 2000 years. The invention of Clovis points around 13,000 years ago is proposed to be near the end of the process, which may have begun before 14,800 years ago according to a kill site at Hebior, Wisconsin.
I think this distinction is just semantic. If 2000 years of human predation eliminated mastodons, mammoths, and all the rest of the megafauna, which occupied North America for more than a million years before that, it looks a lot like "blitzkrieg" to me.
- Pre-Clovis Mastodon Hunting 13,800 Years Ago at the Manis Site, Washington. Science. 2011 ;334(6054):351 - 353.