Since human beings began to interfere with nature's balance, many species have been driven to the brink of extinction. © The Image Bank   “For example, before the mass extinction that marked the end of the Cretaceous Period, mammals had been small, scarce, and generally unimportant,” explains Eldredge. “However, once freed from domination by the dinosaurs, the mammals rapidly diversified . . . even evolving into species that adapted to a marine existence and species that could fly.” The Cause of Mass Extinction #6 is Obvious According to some scientists, Earth is currently in the middle of a sixth mass extinction, and at this time, they are unanimous about the sole cause: human activities.      16 of 17