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JoshuaZ comments on Open thread for December 9 - 16, 2013 - Less Wrong Discussion
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I agree that a few million years is small, and that the low metal content would be a serious issue (which in addition to being a problem for life forming would also make planets rare as pointed out by bramflakes in their reply). However, the real concern as I see it is that if everything was like this for a few million years, then if life did arise (and you have a whole universe for it to arise), as the cooldown occurred, it seems highly plausible that some forms of life would have then adopted to the cooler environment. This makes panspermia more plausible and thus makes life in general more likely. Additionally, it makes more of a chance for life to get lucky if it managed to get into one of the surviving safe zones (e.g. something like the Mars-Earth biotransfer hypothesis).
I think you may be correct that this isn't a complete run around and panic level update, but it is still disturbing. My initial estimate for how bad this could be is likely overblown.
I'm nervous about the idea that life might adapt to conditions in which it cannot originate. Unless you mean spores, but they have to wait for the world to warm up.
As for panspermia, we have a few billion years of modern conditions before the Earth, which is itself already a problem. I think the natural comparison is the size of that Goldilocks zone to the very early one. But I don't know which is bigger.
Here are three environments. Which is better for radiation of spores?
(1) a few million years where every planet is wet
(2) many billion years, all planets cold
(3) a few billion years, a few good planets.
The first sounds just too short for anything to get anywhere, but the universe is smaller. If one source of life produces enough spores to hit everything, then greater time depth is better, but if they need to reproduce along the way, the modern era seems best.
Why this happened on Earth? It is pretty likely for example that life couldn't originate in an environment like the Sahara desert, but life can adapt and survive there.
I do agree that spores are one of the more plausible scenarios. I don't know enough to really answer the question, and I'm not sure that anyone does, but your intuition sounds plausible.
There's barely any life in the Sahara. It looks a lot like spores to me. I want a measure of life that includes speed. Some kind of energy use or maybe cell divisions. I expect the probability of life developing in a place to be proportional to amount of life there after it arrives. Maybe that's silly; there certainly are exponential effects of molecules arriving the same place at the same time that aren't relevant to the continuation of life. But if you can rule out this claim, I think your model of the origin of life is too detailed.
I'm not sure what you mean by this.
Do you mean something like the idea that if an environment is too harsh even if life can survive the chance that it will evolve into anything beyond a simple organism is low?