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If you are at all familiar with the debates between evolution and creationism, then you have undoubtedly heard the creationists' cry for "proof" of evolution (common descent). As should be clear from previous discussion, science doesn't deal in absolute proofs. Scientific theories are provisional and are supported by evidence or data. Proof in science is not the same as proof in mathematics.
Creationists also seem to be demanding direct observational evidence that evolution happened. Obviously, without time travel, this is not possible. Does this mean we can't reasonably conclude that common descent is, in fact, the case? No - no more than a jury can't come to a judgment in a court case without a direct observation of the crime. In fact, "proving" common descent is much like proving a case in a court of law. Suppose you are part of a jury for a murder trial and the evidence presented to you is that:
- the suspect is a large male and the victim is a small female,
- the suspect was found holding a smoking gun and standing over the victim's body,
- the gun is owned by the suspect,
- there were no fingerprints but the suspect's on the gun,
- there were no other weapons found at the scene of the crime,
- the bullet that killed the victim has been shown to have come from the suspect's gun,
- the suspect was seen arguing with the victim before the shooting,
- the suspect had a known hatred of the victim and had threatened the victim in the past,
- the suspect had a history of violent activity that had been directly witnessed (although not at the level of murder),
- gun shots were heard just before the suspect was discovered standing over the victim,
- the suspect and victim were seen running down a dead-end alley right before the shooting,
- and no one else was seen in the vicinity.
However, there was no witness to the actual shooting. Would it be reasonable to find the suspect guilty of murder even though no one directly witnessed the crime? Most people would probably say the answer is yes. Just so with evolution.
While we don't have direct observational evidence of past evolution in action, we do have an abundance of evidence that all support the actuality of common descent. We have the "smoking gun." While you can philosophically argue that the evidence isn't complete, this ignores the fact that, when it comes to the real world, the evidence is never complete. There is always something that can be called into question. Holes in the evidence should not be ignored - indeed, we should try to fill them. But the idea that the huge amount of evidence that supports evolution means nothing if there are missing pieces is ridiculous. There is as much evidential support for the general theory of evolution as there is for any other scientific theory; more than some. So what is the evidence for common descent?
The evidence for common descent comes from a variety of sources and there are a number of ways it could be organized. One productive method is to note that there are two basic types of evidence: direct and inferential. Direct evidence consists of observations of actual evolution and knowledge of the principles involved therein. Inferential evidence is evidence that does not involve direct observation of evolution but from which we can infer that evolution has actually taken place.
The following sections will lay out the evidence for evolution with some commentary on how it relates to evolutionary and creationist ideas. There are literally millions of pieces of evidence and it is not possible to catalogue them all. Instead, you will find here a general overview of the main types of evidence with a few examples. Those interested in exploring the subject in more detail can consult the literature references provided, as well as the links to sites with more information which have been included in the bibliography.
(A bibliographic list of sources and recommendations for further reading will be coming soon...)
This FAQ information provided by Lance F..
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