Not too many years ago it was generally accepted that North American megafauna disappeared at about the same time that humans entered the Americas. The moralistic conclusion drawn in hundreds of popular accounts was that humans despoiled the natural environment and radically reduced the biodiversity of the continent. It was an easy assumption, psychologically satisfying to cheap moralists, and it was politically useful to those activists who were advancing an anti-humanistic form of environmentalism. But, it was based scanty and questionable evidence.
Recently a number of questions have been raised about the idea that humans were agents of extinction in ancient America. It now appears that humans migrated to the Americas much earlier than was previously thought and studies based on different evidence sets have suggested widely divergent times for megafauna extinctions. Scientific American notes that new studies place the extinctions before, during, and after the migration of humans into the Western Hemisphere. So, as in so many other fields what was once settled science has become radically unsettled. Read about it here.
