PALEONTOLOGY
Not until 1796 did scientists begin to entertain the idea that species and whole types of life have gone extinct in Earth history.
In 1796 the French anatomist Georges Cuvier shocked the world by pronouncing that huge teeth (now known to be mammoths and mastodons) were distinct from those of living elephants and that these creatures were no longer to be found alive on Earth. In the United States, our president, Thomas Jefferson (a well-respected naturalist) protested, and launched the Lewis and Clark expedition in 1804, in part, to prove Cuvier wrong: to scout for living mammoths in the unexplored West. A decade earlier, Jefferson had included "mammoth" in his list of American mammals. He wrote,
"It may be asked why I insert the Mammoth [into a list of American mammals] as it it still existed? I ask in return, why I should omit it, as if it did not exist? Such is the economy of nature, that no instance can be produced of her having permitted any one race of her animals to become extinct, of her having formed any link in her great work so weak as to be broken."Extinction became a fact, but the idea of mass extinction was resisted, even into the 1930s, by the majority of earth and evolutionary scientists. Gradually, over the course of decades in the mid 20th century, mass extinction was accepted as fact. In the 1970s, Norman Myers shocked the world by proclaiming that humans are now causing the Sixth Major Mass Extinction. And beginning in the 1960s, but becoming the dominant thought in the 1990s, Pleistocene ecologist Paul Martin led the way in demonstrating, place by place, episode by episode, that humans armed with projectiles and fire effected "overkill" of megafauna on continents and flightless birds and large reptiles on islands whenever our species moved into a new landscape of creatures that did not co-evolve slowly with our technology, thus implicating even pre-agricultural humans, beginning 40,000 years ago in Australia, in this mass extinction of our own making.
Results:Species and entire forms of life have gone extinct. There have been five major mass extinctions, and humans are causing the sixth. Even pre-industrial humans are implicated in the Sixth Major Mass Extinction.