Computer simulations did, indeed, show that our universe is 'fine tunnned', its constants so arranged so as to permit complexity, life. When different constants were inputed into the simulations, the results were boring universes where complexity could not have appeared.
Which raises the question - Why is this so?
Are we living in one of a gazillion universes, one that just happened to 'win the lottery' and have the physical constants that allow life to evolve?
Or is this 'fine tunning' proof of the hand of god, hovering above?
A popular hypothesis to explain this is cosmological Darwinism. If universes can spawn new universes, that's a reproductive process. And in any reproductive process where offspring can differ from their progenitors and one another, evolution is inevitable, because those traits that increase reproductive success will therefore be reproduced more successfully and outcompete other traits. So over the generations, universes would evolve toward traits that maximize their ability to propagate new universes. The idea is that new universes are most likely to be spawned from/within black holes, so universes would tend to evolve toward physical laws that allow the existence of black holes -- and an effective way to create lots of black holes is by creating a universe full of stars. And a side effect of the physics that allow stars to exist is that planets can exist, and that matter behaves in such a way that it can combine into compounds that can interact, and that leads to the existence of life.
Or there's the alternative view that where there's life and intelligence, there's technology, and a sufficiently advanced technology might be capable of creating even more new universes than could be produced by a universe with only black holes and no life. So it could be that universes whose physics are calibrated to allow life and intelligence are more reproductively successful than others.
Maybe one of the requirements of the anthropic principle - one of the "just so" things that has to be the case, or we wouldn't exist - is that FTL travel and communication isn't possible.
Because if it were possible, it would create the possibility of paradoxes that would blow holes in the causality chain that keeps our universe chugging along.
The mistake you're making here is assuming that our current laws of physics are some absolute that dictate how reality happens, rather than merely the best
description of reality that we've been able to approximate so far.
If FTL communication exists, then that means that our current understanding of physics and causality is incomplete and our assumptions about paradoxes are invalid. It's profoundly egocentric to assume that the universe would have to explode if it didn't conform exactly to our current best approximation of physics. Rather, if the workings of the universe don't fit our physical models, that just "explodes" our models, not the universe.
Well, it's entirely possible that the way the laws of physics actually prevent paradoxes is by destroying spacetime in the time-line where a paradox is created.
Based on what? I've been doing a lot of research on temporal physics in recent months, since I'm writing a novel on the subject, and I've come across no theoretical proposals that such a paradox would cause the "destruction" of spacetime. As I said, either the laws of physics are structured so as to pre-empt such a paradox from arising in the first place, or our current laws are incomplete and need to be adjusted to accommodate the reality of causality loops if they do occur.
Indeed, there are existing theories that not only allow retrocausal interaction, but require it. John Cramer and others have proposed that interaction with information from the future is a key factor in quantum processes such as entanglement and the two-slit experiment.
http://articles.sfgate.com/2007-01-21/opinion/17227872_1_quantum-mechanics-universe-particles
Besides, the key mistake you're making is that you're treating the paradox as something the whole universe would perceive and be affected by. That's ignoring the fact that the paradox arises from
relativity -- the different perceptions of relative time by observers in different reference frames. Yes,
some observers in a scenario where two entities were exchanging FTL information would perceive situations where effect preceded cause, but that's because of the interaction of differing frames of reference, differing definitions of simultaneity. The perception of a causal paradox would be a
local phenomenon. Observers elsewhere in the universe would perceive no paradox. Therefore, it is self-contradictory to suggest that the entire universe would be destroyed or otherwise globally affected by such a locally perceived paradox.
