Ah, I meant on our planet. Of course, we wouldn't wonder if it's evident that there is aliens (other intelligent life from another object) at a similar time as when we evolve this level of intelligence. This would be far before we can make technological means to rule out intelligent life on nearby celestial objects, or someone would probably have come up with the question why we don't talk with (the equivalent of) apes and dolphins and such. The other intelligent life would have to be either among us, or visible from where we live (mountains, ocean surface, idk) with whatever we have for senses (like eyesight good enough to observe structures in orbit that are clearly not natural, as an example)