Charles C. Mann, "1491," published on 1 March 2002 via The Atlantic: http://www.theatlantic.com/magazine/archive/2002/03/1491/302445/?single_page=true
hi.. there's lots of room for more input on this (and it may be worth x-posting this question to /r/AskAnthropology), but meanwhile, you may be interested in this brief exchange from yesterday