I found this general article:

http://www.mnsu.edu/emuseum/prehistory/northamerica/linked/hunters.html

From the site:

"The effectiveness of the tool making traditions of the Americas are well documented in the bone deposits and hunting sites through out the area. Among many of these sites, horse, mammoth, beaver, sloth, bison, woolly mammoth, mastodon, and saber toothed tiger can be found in just one site. Even the North American native horse was driven to extinction by the North American Hunters (the horse species was not reintroduced until well into the Spanish Conquest)."

And here's a review of Tim Flannery's "Eternal Frontier". Ellis mentioned he was Australian of the year. If you haven't read the book do so. I'm sure it'll strike a chord.

http://skepdic.com/refuge/flannery.html

From the review:

"Flannery does not think it was climate or coincidence that the three major human invasions of North America were followed by mass extinctions of large mammals. The European invasion may look more egregious than the others because the slaughters are more easily documented, there were many more European invaders than there were Asians in the earlier migrations into North America, and the Europeans brought an abundance of germs and guns. The first settlers only had spears but they wiped out the mastodons and mammoths. They wiped out the horse, too, but they killed these animals for food, thinks Flannery. Europeans killed buffalo for fun. They also shot and killed millions of carrier pigeons for fun. Proving they were not completely senseless savages, however, they shot Indians for land and sport."