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byrnema comments on Planets in the habitable zone, the Drake Equation, and the Great Filter - Less Wrong
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I agree.
My perpective was that it is surprising that the entire universe is only 13.7 billion years old (WMAP) while the Earth is already 4.5 billion years old and it took about that amount of time for intelligence to evolve.
Science has taught us that we're usually not special, but if our evolution already took a third of the time of the entire universe's existence, it seems we're exceptionally early. In comparison, a human lifetime is 60-100 years and I was born approximately 400-600 lifetimes into the cumulative period of human lifetimes which seems much more random than '3'.
Given the information that we are in the second or third time span required for evolution, the expected number of alien civilizations doesn't have to be zero to expect that we're the first. I don't know the relevant statistics, but, for example, it the probability of intelligent life developing in a 3 billion year period is 1/50, we might just need to wait a couple more billion years for the next group. Solar systems are still being born ... aren't we objectively early in that respect?
There's a twist that actually reinforces your point. The first stars (Population III, all dead now) were metal-free. The next generation, Population II, had low metal content. Our Sun belongs to Population I, with higher metal content. So it looks like our Sun belongs to the first, maybe the second, generation of stars that could possibly support intelligent life.
To further that point, it might be worth noting here that "metal" in astronomy parlance means anything heavier than helium. Complex life might conceivably evolve without, say, iron, but life without carbon is much less likely.
Yes - did you see that I linked to the metallicity article? (Astronomers are funny.)
Should have clicked through, in retrospect.
Maybe, but due to anthropic effects, this is one of the times in which we definitely cannot use the we're-not-special rule of thumb. Noting that we happen to have developed gives us absolutely no evidence about the rarity of observers that can notice that they've developed (except that it rules out theories that make it so rare that even 1 observer is unlikely).
Without more information about The Great Filter, most of the probability density does not reside in such perfectly balanced orders of magnitude (like 2% per 3Gyr-galaxy) to make us happen to be first. Though it's an open possibility that we're the first but not the only life that will develop, it's extremely unlikely that two huge numbers that could conceivably be orders of magnitude apart, happen to line up so closely.
I'm not sure I follow your last paragraph. What are the two huge numbers in this context?
The numbers I have in mind are something like: total number of planets and probability of any given planet to allow life to flourish across the galaxy. These numbers are independent. You could start with 'region of space' or involve time, but the numbers will still be independent. (i guess I should have said a huge and tiny number balancing when multiplied)