As there seems to be an ongoing debate on Joeuser about evolution, I've decided to write a little article which clears up a few common mistakes, and answers a few objections against it.
1. What is Evolution?
Evolution is a scientific theory which accounts for the diversity and change in populations of organisms over time. Or, in the words of noted Evolutionary Biologist Dr. Douglas Futuyma:
"Biological evolution is...change in the properties of populations of organisms that transcend the lifetime of a single individual."
Having a proper definition of the subject of the discussion is the first step toward having a coherent debate. Failure to have a common understanding frustrates the entire endeavor, and leads to fallacies such as the straw man argument.
Here are some common examples of what evolution is not and does not say which stem from a faulty definition:
1. Evolution does not attempt to explain the origin of life.
It merely attempts to explain the diversity and change among organisms. As such, it is neither intrinsically for nor against the idea of a "creator."
2. It does not say humans evolved from monkeys.
Rather, humans, apes, and monkeys all had a common ancestor which gave rise to the split we see today.
3. It is not Materialism/Atheism, and it does not logically lead to them.
Materialism is the belief that nothing exists except physical matter ('material'). Now, some materialists will point to evolution to show that immaterial causes (e.g., God, the soul, etc.) are unnecessary. However, while evolution does explain the diversification of life over time using only material causes, that does not mean that immaterial causes don't exist, only that evolution doesn't need them. Thus, people who claim that evolution is, or necessarily leads to materialism simply do not understand what the theory of evolution is, or what materialism is, or both.
A nearly identical answer can be given for Atheism.
4. Evolution is not a theory in the colloquial sense of the term.
A scientific theory (such as evolution) is a well supported body of interconnected statements that explains observations and can be used to make testable predictions. It is not a casually assembled collection of ideas, or an uninformed guess at how a system might work.
2. "There is no good evidence for Evolution"
People who say this usually have not bothered to look very hard, as Google has made it easier than ever to find nearly anything with minimal effort.
Here's one of the more helpful compilations of evolutionary evidence I've come across: 29+ Evidences for Macroevolution
This (lengthy) article considers modern evidence from Morphology, Anatomy, Molecular Biology, Genetics, Biogeography, etc, and analyzes the theory from several different angles and on different scales along with common objections. As such, it is very useful for showing how the entire theory fits together as a coherent whole.
For example: Evidence from our DNA
"Retroviruses (like the AIDS virus or HTLV1, which causes a form of leukemia) make a DNA copy of their own viral genome and insert it into their host's genome. If this happens to a germ line cell (i.e. the sperm or egg cells) the retroviral DNA will be inherited by descendants of the host...In humans, endogenous retroviruses occupy about 1% of the genome, in total constituting ~30,000 different retroviruses embedded in each person's genomic DNA."
The prediction is that if the theory of Evolution is correct (monkeys and humans have a common ancestor), we will be able to find insertions of this viral DNA which we share with them. From the article:
"There are at least seven different known instances of common retrogene insertions between chimps and humans"
This of course fits perfectly with the theory, and you'd be hard pressed to give any other answer for this finding.
It is but one nugget in an unapologetic mountain of good evidence which is certainly avaliable for those who are interested.
3. "There is an Atheistic monopoly on ideas in the scientific community; so of course Evolution is the only supported theory."
First, this view ignores the arguments from people such as Francis Collins (Director of the Human Genome Project) and Kenneth Miller (Biologist and Professor at Brown University) and many others who are most assuredly not Atheists (Collins is an Evangelical Christian, and Miller a Catholic), yet still firmly believe in evolution. In fact, both of them have written books about Evolution and its compatability with religion.
Second, there have been numerous attempts to provide alternate theories to evolution, or do away with evolution alltogether. However, they have failed to convince the scientific community simply due to the lack of conclusive evidence. Here are two examples:
Michael Behe is a Professor at Lehigh University in Pennsylvania, and advocate of the theory of 'Irreducible Complexity'. In 1996, he published a book called "Darwins Black Box", in which he attempted to show that certain formations in biology are too complicated to have evolved, rather, they must have been 'designed.' He states these formations (such as the flagellium bacteria use to swim, or the blood clotting system in humans) are similar to a mousetrap in that they need all the parts together to work properly, and are too complicated to have completely assembled themselves together by chance.
It's a very old argument, but it has a certain elegance to it. Unfortunately it's also fallacious. Like a mousetrap, the parts of these cellular systems have uses outside their standard assembly. So, because the incomplete formation isnt 'useless' (to paraphrase Ken Miller, you could use an incomplete mousetrap it as a catapult), the individual parts can serve other functions in the organism to be later assembled into a more complicated system. Indeed, the different parts of the flagellum do serve other functions in the cell, similarly with the blood-clotting "cascade."
Essentially, even though Behe's book was very popular, his argument doesn't logically hold together, which is precisely why it is not accepted as a valid theory.
Another high-profile example is the 2005 trial Kitzmiller vs. Dover in which the Dover-area (Pennsylvania) school board attempted to defend their decision to allow 'alternate theories' in Science classes, specifically the theory of Intelligent Design (of which the above-mentioned Michael Behe is a strong proponent).
The transcript of the trial is avaliable here: PDF
Its a fairly long read, but quite funny in some places and well worth the time. The wikipedia article is also good: Wiki
The Judge's closing remarks are telling: "The breathtaking inanity of the Boards Decision is evident when considered against the factual backdrop which has now been fully revealed through this trial." Ultimately, the evidence presented (by Behe, and other high-profile Intelligent Design advocates) was found 'wanting', and thus it was deemed unconstitutional to teach in the classroom. It is also worth noting that the judge was appointed by George W. Bush, and is a Lutheran. (Again, I highly reccommend reading the transcript of the trial.)
These two theories (Irreducible Complexity and Intelligent Design) were perhaps the best contenders to take out Evolution, or at least steal its spotlight. Both of them have had many people/books/articles behind them, and Ben Stein even made a movie (Expelled) about Intelligent Design just last year. Yet these theories ultimately fail to hold up when scrutinized. An atheistic monopoly didn't censor them, they collapsed because they don't logically work.
Thus, the Theory of Evolution is just what it says it is: A well supported body of interconnected statements that explains observations and can be used to make testable predictions.
Hopefully this clears up a few things, feel free to leave comments.