Sydney- I think you missed the point of my ranting. The big seperation between our ecology and any that might appear on other planets is origin- by accepting evolutionism and spontaneous life generation theories, we're assuming that all life on earth has one individual ancestor, so the entire time of life's existance on this planet- a mere blip in the astrological sense of things- has been spent slowly diversifying that. Of course life on earth has certain rules that apply to all creatures- the similarities were there to begin with, differences are what take time to produce. If life on another planet had a different origin, the chances of it being EXACTLY the same as ours, the only way that subsequent evolutions of it could even have a chance of resembling us, is astronomically small.
I agree with you that environments dictate evolutionary paths, but remember, we're talking about individual species here, not entire ecosystems. You're absolutely right- on a planet similar to our own, the ecosystem would be extremely similar, but there's a lot of room within those parameters for variance in the components- the individual species. Look at Madagascar. The natural environment there is almost identical to that of mainland Africa, but in just a few hundred thousand years, next to nothing on the evolutionary scale, the individual species have evolved completely differently, while still funcitioning the same way overall. Instead of having burrowing rodents, it has anteaters and in-land digging turtles, instead of using birds to spread fruit seeds, it majoritively uses Lemurs. And all these differences, even with a common origin. Yes, the ecosystem would be roughly the same on a similar planet, but there could be all sorts of crazy combinations of components to it that would still work, and without a common origin to earth it's very likely that none of them would resemble ours. To assume that life in other parts of the universe would evolve similarly to our own is like watching one game of chess and assuming that every game ever played had the same final positions for the pieces. Yes, the players will always be out for the same goal, but there are a lot of ways of accomplishing it.
Oh, and, last I checked, four limbs loses out pretty badly to six when you're looking at the majority vote on earth. Pound for pound, insects rule this rock.
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