[danaris]

> The big filter in terms of population is our ability to terraform other planets and since terraforming takes thousands of years, staying alive on earth with stagnant birth rates is an important part of it until the terraforming is complete.

I think this is actually very crucial, and something too few people appreciate: We need (or will need, at some point; the carrying capacity of the Earth is actually quite a bit more than 8-10 billion, we just need to be better about distributing resources) to keep population from continuing to grow forever on Earth until we have reliable means of colonizing other planets.

This also means we need to avoid getting too far in life-extension/physical immortality research before then! If we can actually achieve physical immortality, but we're stuck on Earth, at some point we will have three choices: stop having kids, start killing each other off in significant numbers, or start running out of resources.

(That is, of course, entirely separate from the concern that life-extension treatments will only be available to the very rich.)