Evolution to Perfection: Lamarck was a proponent of spontaneous generation, the belief that life can appear spontaneously from inanimate materials and then gradually change into more complex forms through a constant striving for perfection.
He believed that the ultimate product of this goal-oriented evolution was the human race. His theory, now known as Lamarckianism, was based on the belief that evolution was mostly due to the inheritance of acquired characteristics as creatures adapted to their environments.
Inheritance of Acquired Characteristics: Lamarck's assertion was that that evolution occurred when an organism used a body part in such a way that it was ultimately altered during its lifetime and this acquired change could be inherited by its offspring.
For example, Lamarck thought that giraffes evolved their long necks by each generation stretching further to get leaves in trees and that this change in body shape was then inherited. This is the inheritance of acquired characteristics, and although an appealing theory that, on the surface seems to make sense, it is absolutely without merit.
Catastrophism: George Cuvier (1769-1832)
Because of the weakness of Lamarck’s theory, it was relatively easy for the French scientist, Georges Cuvier, and other critics to discredit the idea of inheritance of acquired characteristics.
Critics were quick to point out that if Lamarckianism was correct, the children of cowboys, who have developed bowed legs as a result of a lifetime of riding horses, would be born with bowed legs, and the children of professional weight lifters would be born with enlarged muscles. It is obvious that these things do not occur.
Although he criticized Lamarck, Cuvier did not reject the idea that there had been earlier life forms. Cuvier was actually the first scientist to document the extinction of ancient animals and was an internationally recognized expert on dinosaurs.
However, Cuvier also got in wrong, in that he rejected the idea that the previous existence of dinosaurs implied that evolution had occurred. He believed that species were fixes and did not change. So, as an early paleontologist, how did he account of the existence of many extinct species?
Like many other scientists of his day, Cuvier advocated the theory of catastrophism. This theory was based on the assertion that there have been violent and sudden natural catastrophes such as great floods and other very sudden physical changes to the earth.
Organisms living in those areas where these sudden, violent changes had occurred were often killed off and replaced by new life forms moving in from other geographic areas. The fossil record of this type of region would show abrupt changes in species.
Uniformitarianism: James Hutton (1726 - 1797) & Charles Lyell (1797 - 1875)
Charles Lyell, an English lawyer and geologist had carefully examined European geological deposits and concluded that catastrophism theory was wrong. Although such catastrophic events may rarely occur, Lyell believed that there was more commonly an accumulation of progressive changes over long periods of geologic time.
Lyell documented the fact that the earth must be extremely old and that throughout time the planet has continually undergone processes that change and shape the land, including erosion, earthquakes, glacial movements, volcanoes, and even the decomposition of dead plants and animals. The theory that resulted from Lyell’s observations was called uniformitarianism.
The theory of uniformitarianism had originally been developed by the Scottish geologist, James Hutton, who also proposed that the natural forces currently changing the shape of the earth's surface had been operating throughout time in much the same way.
Paving the Path to Darwinism
An understanding of uniformitarianism was instrumental in leading Charles Darwin to his astute observations on biological evolution in the 1830's.
In 1858, Charles Darwin and Alfred Wallace released a joint scientific paper which introduced the concept of evolution by means of natural selection. This paper, along with Darwin’s subsequent publication, “The Origin of Species”, changed the way science and society explained events in our natural world.
- Brown, Bryson (2007) Evolution: A Historical Perspective. Greenwood Press.
- Campbell & Reece (2005) Biology, 7th Edition. Pearson.