Theory of evolution

A theory of evolution is an attempt to scientifically explain how evolution occurs. There are countless theories of evolution, many of which are compatible with one another. Others, such as Lamarck's theory of inheritance of acquired characteristics, have been falsified.

The three most widely held theories of evolution are (1) Sudden Creationism, (2) Intelligent Design, and (3) Darwinism. Sudden Creation, believed by 4 out of 10 Americans, essentially denies that evolution occurred at all; all forms of life were created by God at the beginning of the world; dinosaurs never existed. Intelligent Design, believed by 3 or 4 out of 10 Americans, acknowledges the validity of the fossil record; all forms of life were created by God close to the time they first appear in the fossil record. Darwinism, believed by 1 out of 10 Americans, denies that God had anything to do with the appearance of new species; either he set up everything "on automatic" after initiating life, or there is no God.

In popular usage, "the" theory of evolution refers to the various theories proposed by Charles Darwin, notably the theory of common descent, and the theory of evolution by natural selection. It also refers to the modern Darwinian theory that combines evolutionary theory with the science of genetics.

Natural selection suggests that a species adapts to changes in the environment, as a result of randomly occurrring genetic mutations. These mutations can alter the individual's physical shape or the inner workings of the body so that organs may change their shape or size or the immune system may develop a different reaction towards disease. After the mutation has occurred, it's up to nature to test that change in real life. If the change benefits the individual, the individual is most likely to have a better chance of survival. Otherwise, the individual will most likely die and the faulty mutation will be discarded. Often these processes last thousands of years due to the slow rate of mutations as well as the lifespan of the individual, although it seems that in some cases evolution can occur unbelievably quickly, within a few generations (Punctuated Equilibrium). /Talk1

Evolution by natural selection has been observed so many times that it is now considered a fact.

No, many Darwinists regard Evolution by Random Mutation to be true, but scientists still consider it a theory. Let's not confuse Fact, Theory, and Law. A fact is you see the sun rise and go across the sky. A theory is, e.g., that the sun revolves around a stationary earth; or, that the earth revolves on its axis. A law is, e.g., that a massive object subject to a radial force inversely proportional to the radius will travel in an ellipse. -- Ed Poor

There have been numerous observed cases of speciation, especially in plants (see [link] for more details). Speciation has not been observed per se in vertebrates?, although there are numerous examples of no-longer breeding subpopulations.

Important concepts in evolution:

• Common descent
• Gradualism
• Natural selection
• Sexual selection
• Speciation

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