This exploitation has reached such extremes that presently it appears that some hundreds of thousands of species will be extinguished before the end of the century.
Rock samples taken from the remains of an asteroid about twice the size of the 6-nuke-wide asteroid that eradicated the dinosaurs has been dated to be 3.47 billion years old.
Still, Krech attributes secondary if not primary responsibility for the extinctions to the Paleoindians, arguing that humans have produced local extinctions elsewhere.
Other features, however, show experts that Pakicetus is a transitional form between a group of extinct flesh-eating mammals, the mesonychids, and cetaceans.