Humans began to spread across North America around 12, 000 years ago, as the climate became warmer. During the same period the large mammals that were once abundant in North America, such as the mastodon, the woolly mammoth, and the saber-toothed tiger, became extinct. Thus, contrary to the myth that humans formerly lived in harmony with the rest of nature, it is clear that even 12, 000 years ago human activity was causing the extinction of animal species.
In calling the idea that humans once lived in harmony with nature a myth, the argument presupposes what it attempts to prove, making it vulnerable to criticism.