The fundamental problem is that two sentient perspectives cannot overlap, or knowingly perceive each other. All sentient perspectives are essentially black holes with respect to each other, with corresponding "perception horizons".

We can therefore never have true knowlege of when and where we might encounter another sentient perspective. We might assume, by analogy to ourselves, that other sentient perspectives occupy the space around or within other human or animal bodies. But we can't verify it or test a predictive model about it in the same way that we can with other things we can perceive - like every time we drop an egg, we can predictably perceive it fall and break.

In a way, all scientific claims are ultimately claims about what our own sentient perspective will perceive if we follow a certain testing procedure. Whereas claims about when and where other sentient perspectives might arise is an altogether more speculative undertaking. It's not asking a question of what our own perspective will perceive, but rather, what a different perspective will perceive - or whether it even exists, or perceives anything at all.

We know, without any doubt, from our own subjective experience, that the universe is indeed a place where subjective experience exists, and is inherently valueable. Our own desires, hopes, fears, pain, and pleasure make this undeniable. It's just the merging of this type of knowledge with the predicting of where else subjective perspectives exist, where we run into problems. And that is just because we can't knowingly detect the existence or feelings of another sentience - aside from just assuming that it is there.