New life, and new life forms

I think whatever other intelligent life we find in the universe is going to be roughly bipedal because we're going to make it that way; you know how in a lot of sci-fi settings there's a long-vanished "progenitor" race that leaves behind a bunch of artifacts and may have genetically "guided" other species to sentience?I think that's going to be us. I think we're the first intelligent race in the galaxy. Maybe in the universe. I think solar history indicates that our sun is probably the second star in this neck of the woods; you couldn't have life until after the first star because you need a dying star to produce elements heavier than helium. So I think we probably evolved about the earliest it was possible for intelligence to evolve.Just my speculation of course. I think Bluejay is right that other life in the universe is likely to be carbon-based, since (as my organic chemistry textbook reminds me) silicon-based life that tried to respirate would exhale silicon dioxide, which is a solid under Earthlike temperatures and pressures! I think alien life will probably have left-handed amino acids since I think abiogenetic conditions probably favor them (but, I wouldn't rule out maybe one in a hundred planets where some kind of d-amino-based life gets an early foothold.) I think they would have something analogous to DNA, but it wouldn't necessarily have to be DNA - the phosphate-ribose backbone and the specific nucleobases seem kind of arbitrary. It's not hard to imagine something like an erythrose-arsenic backbone with funny bases, like hypoxanthine and inosine. Probably reasons why that's a lot less likely, but a lot of this stuff comes down to whatever arbitrary chemistry outcompeted everything else to become the LUCA. It's like, why did Betamax never catch on?Codon substitutions would be completely different. The funniest part of Avatar for me was the notion of inserting human genes into na'vi - they'd produce completely different proteins, even assuming the same 20 amino acids (which there's no reason to.)

Well, they have to orbit the second star in their neighborhood too, or else how could they have planets?I guess what I'm saying is, the full life and death of a star seems to be a prerequisite to forming a life-capable star system, so I don't see how there's much time for any other system to have gotten much of a jump on us. The indication (as I recall) is that the last star, the progenitor of the Sun, formed fairly soon after the formation of the universe, but maybe I'm wrong about that. Given the rate of technological advancement in intelligent species, any intelligence with as much as a million years head-start should be engaging in engineering on a galactic scale by now. We should be able to see their public works projects from here.

I guess the only assumption I feel I'm making is that, regardless of how fast technology develops it develops instantaneously over geologic time. And if we're talking about a geologic-scale time different between another life-bearing world and ourselves that's going to represent an inconceivably vast gulf between our technology and theirs. Well, we're pretty much all going to do that.

Well, I take your points. Obviously there's substantial room for a diversity of opinion on this stuff, and certainly tantalizing hints of extrasolar civilization (like the "Wow!" signal) indicate against my position.You know, but weird synchronicities do happen. Newton and Leibniz independently developed calculus almost exactly at the same time. Edison and Swan invented the same lightbulb.Just sayin'. Like I said I take your points. Well, they shouldn't be too distant. The Fermi paradox is that even assuming a relatively low rate of Earth-like planet formation, and even assuming a relatively slow rate of evolution of complex life forms, and even assuming wildly different timescales that intelligent life could evolve on, and even assuming the incredibly narrow span of time we've been able to look, we should still be up to our nutsacks in alien civilizations. Our galaxy should be a very crowded place but it's not. I suspect that's because we're the first ones to arrive at the party.