[RAM-bunctious]

Not that I'd call myself a buff, but I don't think my knowledge of larger numbers makes 10^24 a small number in any absolute sense. Cryptographic keyspaces are deliberately designed to be unfathomly large, whereas the number of stars in the universe is simply an observational fact. The number of stars really is huge in a human sense, as much as that's worth anything. There are more stars than there are grains of sand, etc.

The fact that we exist to discuss these odds means that whatever the probability distribution, at least one instance of life has occurred. Not only that, but life arose and eventually led to intelligence at our level - something that appears to be rare even on our own planet, but achieved relatively quickly all things concerned (only a few hundred million years).

While the anthropic principle guarantees that we observe intelligence as we're defining it (since we include ourselves), I agree that doesn’t mean intelligence is inevitable or common. A more likely modelling in my opinion is that worlds of microbial life are abundant, worlds with complex multicellular life is rarer, and intelligent civilizations are rarer still. Given the distribution of intelligence levels on Earth, it seems unlikely that we simply passed every constraint while no other planet gets close. Also, if we observed a planet with humans as they were 100,000 years ago, would we even consider them intelligent life? Probably just as intelligent as modern-day humans if raised the same, but literally nowhere near our technological level.

When scientists evaluate whether soil can support certaing thing, they don’t treat each factor (like pH, moisture, nutrients, microbial conditions) as independent hurdles that must be overcome one by one. Instead, they see that multiple factors interact in complex ways. A deficiency in one area (e.g., nutrient content) can be mitigated by another factor (e.g., microbial activity enhancing nutrient cycling). If you extend this to conditions in which life might it arise, it suggests to me that planetary habitability may be more like a network of contributing conditions rather than a checklist -- actually much more difficult to caclulate?

Also, mostly as an aside, we also have the advantage of knowing that life and then intelligence arose relatively quickly once conditions stabilized - only a few hundred million years. n=1 but I think this is a promising indication on where any variables might lie.