Ancient humans started destroying the abundance of the seas by slaughtering numerous species of animals, changing a delicate balance that was tipped further by excesses of the modern age, a recent study finds. Effects of the environmental damage caused by the disappearance of key species, such as sea turtles in the Caribbean and sea cows off the coast of Australia, continue to be felt at present. "The notion of the native peoples having a benign impact on the environment has been challenged,' says Charles Peterson, professor at the University of North Carolina, USA.