^^
Well, first off, nobody said it was
impossible, only that it was incredibly unlikely and implausible without a damn good explanation, an explanation that I seriously doubt any of us is going to hear from the Beebs and their staff. To turn around what
Pudding ended with, it may be fiction, but it's
science fiction, and that means you can come up with all kinds of wildass ideas
if you also come up with rational explanations for them. Berman obviously doesn't understand this, from his statement that "it's science fiction, which means you can get away with anything." Well, that may work for fantasy, but not for science fiction (heck, it doesn't even work for fantasy, because once you establish something fantastic, you
still have to stick to the rules you've established unless you just don't give a damn about your readers, in which case I recommend a new job ...).
The hoary old argument still doesn't work, either; you know, the one that says, "Well, if you accept warp drive, time travel, transporters, etc., you
have to accept all the rest or else you're a hypocrite." There's a difference between completely fantastic fictional science like those (and at this point, many of these are becoming closer to reality anyway; don't forget, too, that many of these were originally -
intentionally - based upon concepts that science had established, to the point of talking with real scientists, even well-known ones; they weren't just pulled out of Gene's ass), and unexplained anomalies that completely contradict basic science that we
do know, and have established for hundreds of years. Sure, we only have the comparative biology of our own planet to work from, but that includes millions of years and millions of species, and hundreds, if not thousands, of different environments, all wrapped up in one large, observable test lab. Over millions of years, the processes stabilize unless there is a shift in the environment; one can make
reasonable extrapolations to other circumstances that one knows aren't
radically different from our own, which brings up the next point ...
Keep in mind that
Trek concentrates on alien life that, for the most part, is biologically compatible with our own. Not
genetically (although that certainly happens more often than is plausible, too), but biologically; these 'alien' lifeforms all breathe oxygen - for the most part, are carbon-based - for the most part, and we and they can live in each other's environments without adaptation. It's that whole "Class M" thing: they're not out there looking for
new life; they're out there looking for life
like us (a pretty narrow-minded approach, when you think about it, but it's more easily filmable, right?

) The likelihood that biologically-compatible life will develop in biologically-
incompatible environments is even slimmer than that biologically-compatible species will also be
genetically-compatible. Again, look at all the species on this planet alone, from human beings to other mammals to reptiles to crustaceans, and how many of these different species can interbreed? It's an
awfully short list, right? The same thing goes for the evolutionary process, particularly when it comes to competition. In
all of the environments on this planet alone, there is competition, and no one environment maintains truly competing species for long; one always wipes the other out, or forces it into another area. That's just the way it is, and with it occurring in
every known environment, it's a reasonable assumption that this is always the way it's going to happen, unless there's a
good reason for it not to be so; it's not like the mammals called the reptiles and said, "We're going to go with the 'competition model'; you want to do that, or are you guys going to try symbiosis?"
I agree,
Trek shouldn't be a research paper; it's about entertainment (well, that's what they
say about ENT, at least ... ). But because of what
Trek is, a sci-fi show as opposed to a cop show, a lawyer show or a sitcom, when you start mucking about with known scientific principles, things that are taught in grade school, there should be a reason beyond "we thought it would be kewl." Maybe they
did, but that doesn't absolve them from the responsibility to, in the story, create a reasonable-sounding explanation. If the Xindi are supposedly 5 sentient species from the same planet, there should be not just a scientific reason for that, there should be a
dramatic reason for it. These 5 species are the "gun in the desk drawer": if you are going to make this point, then you had better do it because it's going to be important to the story. The Xindi could have been one violent, paranoid species, and there would be plenty of potential for conflict and understanding; split them into 5 species, against common sense and scientific rationale, and there needs to be a damn good reason for that to be the case.
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I have to get a Cliff's Notes version of Ptrope's posts. - Kirk's Glasses