Who Ever Said That?
When "debates" about evolution arise in the popular media, I find myself engaging in a constant fight to right the wrongs — the myths if you will, or more precisely, the misinformation — that are perpetuated by a very vocal and very ignorant crowd of "journalists".
Humans did not evolve from apes. Darwin never conjectured that humans descended from apes. He conjectured that humans and apes were co-descended from a missing ancestor — the infamous "missing link".
Evolution is not Darwin's theory. "Evolution" is not something that Darwin came up with. The fact of evolution, which is tied to geology and biology and history and physics, was explained by Darwin in his "Origin of Species" and in his "Descent of Man". His works were theories about the mechanism of evolution. In the same era, other theories of evolution had been developed, for example by Lamarck, who conjectured that evolution happened as "exercised" traits were passed from parent to offspring. Let's say that I developed a strong right forearm from playing tennis — on Lamarck's analysis, my children might likely have strong right forearms as well. (Simple and disingenuous example, but illustrative.) Darwin's theory is very different.
"Fittest" means best adapted, not strongest. To Darwin, what counted as "fitness" involved a creature's ability to survive in its environment. "Fit" does not necessarily mean strong or robust. The phrase was coined by Herbert Spencer, who applied it to economic competition, a closer match to modern misuse, but certainly not Darwin's intended use. Darwin preferred "natural selection" over the phrase "survival of the fittest", for in natural selection he posited that those species best adapted to their peculiar environments would survive to pass on their genes / traits. Were Darwin to restrict "fit" to "athletic" or "strong", as modern mis-interpreters push, he would have ignored the significance of environment in favor of individual characteristics. His emphasis was on environment, which is partly what distinguished his theory so radically from Lamarck's.
Lamarck, as noted, emphasized the role of the individual in developing new traits. Darwin's theory incorporated data about the species' physical surroundings to explain how traits develop and survive. This was something of a revolutionary break.
Today, Darwin's explanation of the process of evolution is not widely accepted. Many more robust competing theories have emerged as biologists and geologists have uncovered further fossil evidence and developed better genetic theories. For example, Stephen Jay Gould advanced a theory known as "Punctuated Equilibrium". His theory addressed anomalies in the fossil record that could not be explained by Darwin's theory. Darwin's theory posits a continuous process. The fossil record does not reflect such continuity. Gould posited that species tend to go through rapid periods of change, followed by long periods with little variation. (There are lots more details, of course. The point is that it's not Darwin or bust.)
Explanations of evolution have changed radically since Darwin's time. This is normal: this is how science moves. Darwin only had access to superficial data, like the shapes of various animals and fossils and other basic physical attributes. Today, evolutionary theory appeals to genetic theory for much of its explanatory power. Today we talk about DNA, carbon dating, genes and so forth when we talk about the process of biological evolution. This is vastly more robust than the superficial explanations that Darwin posited.
There are no "Darwinists" anymore. Maybe there's a crackpot or two out there, but there are no respected biologists or zoologists pushing for Darwin's theory. Today we talk of the "modern synthesis", which incorporates some of Darwin's ideas of selection with modern genetic theory.
Hence, for ID to compete, it must take on genetic theory, etc. Proponents of ID, to be taken seriously, must address things like carbon dating, DNA evidence, and so on, because those are the concepts that underlie modern evolutionary theories. However, to challenge something like carbon dating, for example, requires challenging modern particle physics; it will be very difficult to demonstrate that particle physics is bunk. The advances that led to the possibility of carbon dating are the same advances that led to chemotherapy, and were in the family of advances that led to the possibility of computer chips (namely, advances in quantum mechanics.) So, in an important sense, evolutionary theories are intimately intertwined with a wide array of hard sciences. To "compete" on the level that ID appears to want to compete, they have a lot of hard physical science to re-explain. (I will issue a personal challenge to any ID proponent to re-explain particle physics and quantum mechanics in such a way as to tear down carbon dating, yet retain the possibilities of modern computing. And I point out the deep irony of anyone blogging about this.)
The most important point to emphasize is that "evolution" is not a theory. "Evolution" describes trends identified in the fossil record — among other things. Darwin's theory of Natural Selection represents one attempt to explain observed variation and to explain geologic / fossil data.
For "Intelligent Design" to compete as an evolutionary theory, it would need to posit a mechanism that explains species variation and explains the same set of geologic / fossil data that other evolutionary theories attempt to explain. Furthermore, to properly count as a theory, Intelligent Design should be predictive (much as general relativity or Newton's mechanics can be used to predict outcomes of experiments.) A good theory, generally speaking, is both explanatory and predictive.
The super important point: Intelligent Design, if it wants to be a competing evolutionary theory, must attempt to explain the same data as other competing evolutionary theories. If proponents of ID want to discredit the fossil record or discredit genetic theory or discredit physics, biology, and so on (as it sometimes seems), then they cannot reasonably expect to be taught along side with any competing evolutionary theory.
Furthermore, if any teacher in the world teaches "evolution" as a synonym for "Darwinism", I'd like to have a little chat with them.