EARLY THEORIES OF EVOLUTIONSource: Biology: A Study of Life (1990)Objectives:
1. Outline Lamarck's theory of evolution.
2. Describe Weismann's experiment to show that acquired characteristics are not inherited.
3. Explain the principle of natural selection.
4. List the six main points of Darwin's theory of evolution.
5. State the chief weakness of Darwin's theory. 6. Explain the theory of punctuated equilibrium.
Up to this point in the chapter you have read some of the scientific evidence for believing that organic evolution did occur. However, the evidence for evolution does not explain how or why it occurred. The remainder of the chapter deals with theories of how evolutionary change is brought about.
28-9 Lamarck's Theory of Evolution
One of the first theories of evolution was presented by the French biologist Jean Baptiste de Lamarck in 1809. From his studies of animals, Lamarck became convinced that species were not constant, but evolved from preexisting species. He believed that evolutionary changes in animals were caused by their need to adapt to changes in the environment.According to Lamarck's theory, evolution involved two principles. The first was his law of use and disuse.
According to this principle, the more an animal uses a particular part of its body, the stronger and better developed that part becomes. Also, the less a part is used, the weaker and less developed it becomes. An athlete, for example, develops the strength of certain muscles by constant use. On the other hand, muscles that are not used tend to become smaller and weaker by disuse. The second part of Lamarck's theory was the inheritance of acquired characteristics. Lamarck made the assumption that the characteristics an organism developed through use and disuse of various parts of its body could be passed on to its offspring.
According to Lamarck, the long neck of the giraffe would have evolved in the following way (see Figure 28-11). The ancestors of modern giraffes had short necks and fed on grasses and shrubs close to the ground. As the supply of food near the ground decreased, the giraffes had to stretch their necks to reach leaves higher off the ground. Their necks then became longer from stretching, and this trait was...
The big push between the Creationists and the Evolutionists is of more recent vintage.
Seriously, I suspect Lamarckianism has been dropped from the biology texts by the publishers simply to avoid risk of loss of sales as state laws on the matter are "reinterpreted".
We have some Freepers with experience in the textbook business. They might know. I just did a quick google.com search and didn't find anything one way or the other although it has popped up in some of the discussions concerning banning of either Creation stories or Evolution (both having been banned at different times by different folks for various reasons).