Evolutionary Biology/Jean-Baptiste Lamarck
Jean-Baptiste Lamarck (1774 – 1829) was a French botanist who proposed two ideas that had great impact in the theory of evolution. Lamarck did not believe that a species could become extinct. Instead, he saw the idea of extinction as every member of a species evolving into another species. He believed that change was brought about through use and disuse and inheritance of acquired characteristics. This was the first time that a mechanism was proposed in order to explain how a change in a species occurred.
The first idea of use and disuse is only the first part of Lamarck’s revolutionary thought. It is referred to as the 'First Law' of his publication, Philosophie Zoologique. . The use or disuse theory explains that the parts of an organism that the organism uses most will undergo hypertrophy and will become more developed. Hypertrophy is the growth of a specific organ or tissue. So by this idea, the more an organism uses a part of its body, the larger and more developed that part will become. The parts of the organism that are not used as much undergo atrophy and begin to degrade from lack of use. This means that the part of the organism will get decrease in size due to the lack of use for that particular part of the organism. This is the beginning of the idea of inheritance of acquired traits.
The inheritance of acquired traits, also known as his 'Second Law' in Philosophie Zoologique, is the idea that the traits of an organism that undergo hypertrophy will be inherited by the next generation. This hypertrophy suggests an adaptation to the environment that can be passed on to the next generation through the genetic code of the organism.
Even though Lamarck made astounding progress throughout his life, this theory of evolution has been revised by following studies. The Lamarckian view of evolution is seen as a tendency for a species to reach perfection where it is actually simply adapting to their environment in a single generation. We now know that the inheritance of acquired characteristics is not an actual mechanism of evolution.
Darwin saw that Lamarck had some very good ideas that could lead to evolution. Many of Lamarck’s ideas can be seen in Darwin’s Origin of Species. Lamarck was a believer in immutability. Darwin used this idea to further his research on how species were indeed mutable. Darwin also used Lamarck’s inheritance of acquired characteristics as support for his natural selection idea. He used Lamarck’s basic structure, but changed the theory Lamarck used into the actual mechanism of natural selection. Instead of saying that the traits one organism acquires during its lifetime to better its success, Darwin said that these characteristics would eventually reveal themselves in offspring and later generations instead of in the present organism. These were just some of the ideas Darwin modified while writing the Origin of Species.
- Campbell, Reece. Biology, Sixth edition. Benjamin Cummings. 2001.