[kahljorn]

"The common belief in extraterrestrial life fits this pattern, too"

Um? I don't know so much that people believe in extraterrestrial life so much as they believe in the possibility of extraterrestrial life( i think believing in your own life kind of makes the belief in other life a logical step) . Same with evolution. It seems alot more likely and alot more logical than anything else. If your argument is that people act on what they assume is correct or more logical are ignorant or whathaveyou, than that's just fine, but I'm sure it's the exact same thing you are doing now.

"I'd venture to say most people don't spend a whole lot of time investigating this argument or questioning common descent."

I don't think they care, and why should they? According to you it's all bullshit (and I use that term loosely) anyway.

"We find many different ways to think of ourselves and our actions as meaningless or immaterial. Doing so takes a lot of moral pressure off our every day decisions. "

I agree, but I don't think the belief in evolution fits this pattern, if anything it supplies the exact opposite. Especially when you start to look at dawkins use of memotics as some type of evolutionary component you can see this pattern.

"Well, that's not the common conception of our existence is it? "

How could it be? Regardless of what consequences our lives have on this little planet, the universe is alot bigger (and existence even bigger) . Lying to yourself isn't going to make anything better-- if anything it creates more problems. The fact of the matter is, our life here is inconsequential to eternity, and it doesn't really matter what we do here because some day it will all be wiped away; whether if it's by God and his Rapture or the Universe collapsing into itself (or the sun turning into a red giant and engulfing the earth) the result will be the same.
Even if you were to argue all that, the universe was still built on nothingness-- that's just something that needs to be accepted by any observer of the universe.
You rely too much on the universe outside of us(for no good reason). The items you stated were all outside of humanity except the first one which I agree with. You need to start thinking more on the here and now (selfishness is a great tool for the selfless and the poor, I think). To some extent maybe what you said is true, however, the effects of things outside of us also have 'universal consequence' which essentially negates our own(like the space outside of us that we can't really breath or survive in for example, or ET life if you want to take it to that length-- there's just too many other influences or POSSIBLE influences, really). I don't know, what you said is pretty much just stupid. Humanity isn't the only force in the universe. Assuming we are God's favorites is rather arrogant. God loves all his children.

How would we be lucky to be here? If anything it's just a natural part of the universe that life exists in certain enviroments. It's just as insignificant as mold appearing on old bread. The only reason to feel "Special" is if God or something like that put us here. Is that what you're turning your argument towards?
In a religious sense that's a horrible way to think. Embracing the devil, are we?

"I choose happiness because it is the only thing over which we each have individual sovereignity."

Maybe in some pure form, sure, but this isn't a pure world. There's alot of unhappy people out there who think all the time. If anything, happiness is a product of unthought.