Mine is probably the most boring: There are many intelligent species in the universe. Faster-than-light travel, however, really is simply impossible, meaning that there cannot exist a truly interstellar civilization. So while some species have probably settled solar systems other than their own through generation ships, suspended animation, time dilation, or whatever, their range of expansion is limited. This means that encounters between species of different planets are rare. Humans will most likely never contact any intelligent alien species, at most one or two. We might, however, discover evidence of their existence through telescopes or something.
I’ve got a similar opinion, although I think it’s more likely that “technological” life is less common. We know that life arose on Earth just about as soon as it was viable for life to arise, but the evolution of eukaryotes took over a billion years, and that event may have only ever happened once. After that, multicellular life took another billion or so years to start evolving. If we imagine that those two evolutionary events are in fact not ‘inevitable’ consequences but instead infinitesimally unlikely chances, it feels like there’s probably a whole lot of prokaryotes in the universe, but significantly less multicellular life.
Adding on to that, there’s been a bit over 100 million years of large terrestrial lifeforms before evolution finally rolled a species that had the qualities to do the kinds of things that humans have done. We’re already seeing how intelligence does not inevitably lead to development of human-analogue technology (Corvids, Cetaceans, other great apes). Many species through land evolutionary history have likely had human-level intelligence, but due to other circumstances didn’t go along a path that led to space exploration. So I think that there are still planets that have complex multicellular and even intelligent life, but no agriculture or other stuff that would lead to industrial-level societies.
I agree that it’s depressingly likely that FTL just doesn’t exist in a meaningful sense, which would form the biggest difficulty in creating interstellar communities.
This is really interesting, what species are meant to have similar intelligence to humans?
Yeah, that’s kind of more like it. We can’t really estimate the intelligence of extinct species that well aside from looking at brain size and other physical circumstantial evidence, but I’m extrapolating from our current and growing understanding of intelligence in non-human animals like dolphins and corvids. We’re increasingly realizing that these species are much smarter than we had previously thought, and the toolmaking, memory, and self-recognition displayed specifically by magpies (I think) means that these traits can evolve outside of mammals.
I’m of the opinion that ‘being human-level smart’ is not something that’s only popped up in humans, but merely that our hominid ancestors were the first to combine that with other relatively rare features like opposable thumbs to allow for unprecedented tool use, and then things just happened from there.
