Part 2 of 5
Nicholaus Steno and Robert Hooke argued for a naturalistic interpretation of fossils. One problem still exited. What to do with unfamiliar organisms that appear in the fossil record.
Today, extinction, the permanent disappearance of a species, is an all too familiar concept. In recent history we have witnessed the extinction of many species due to the human activities of hunting and habitat destruction. As little as 200 years ago many people thought extinction was impossible. Theology fueled opposition to the idea of extinction. People believed that the biosphere constituted a perfect creation. the concept of extinction was contrary to several deeply held Christian beliefs. First, was the concept of divine providence. An all-powerful and all-loving God would never allow any creature to become extinct. This is illustrated in the story of Noah's ark. God would not suffer any species to become extinct and thus ordered Noah to populate the ark with two of each creature. Second, was the idea of plenitude (fullness of nature). God's creation was perfect and an organism's extinction would render it incomplete. Finally, was the concept of a "Great Chain of Being". This chain linked animals to human to angels to God. Extinction would take away links in the chain leading to its destruction.
Thomas Jefferson (1743-1826) strongly believed in the Great Chain of Being. Jefferson and many others argued that the strange organisms found in the fossil record must still exist in unexplored parts of the world. A large fossil claw prompted Jefferson to ask Lewis and Clarke to look for a giant prairie lion on their expedition. This claw was later found to be a part of the extinct giant ground sloth.
The great French anatomist Georges Cuvier (1769-1832) established extinction
as a fact in a historic lecture given to the French Institute in 1796.
Cuvier talked about mammoths, woolly rhinos, giant cave bears, and the
sea reptile mosasaur in his lecture. In his paleontological studies
Cuvier came to recognize what we now call mass extinctions at the end of
the Permian and Cretaceous periods. Cuvier developed the theory of
catastrophism. Cuvier believed supernatural cataclysms occurred before
Noah's flood (antideluvial) and were regional not global.
Stephen J. Gould (1941-2001), American paleontologist and writer, believes that extinction is needed to tell time and is the motor of evolution. If all the species stayed the same there would be now way to tell geologic time. Furthermore, if species didn't disappear there would be no room for new ones to evolve. For example, during the reign of the dinosaurs mammals never got bigger than an ordinary house cat. If the dinosaurs had not died out there is no reason to believe that mammals would have increased in size and, in that case, we would not be here.
It is ironic, that in that last two hundred years scientist have gone from believing that extinction is impossible to establishing that 99.9% of all species that have ever existed on Earth are now extinct.