Humanīs desire to emulate birds led to the development of the airplane. Rockets were an extension to the concept of airplane. So, our spacefaring is almost directly linked to the existence of birds.
Birds spend much energy to fly. I think we could say theyīre on the limit. Had Earthīs gravity been slightly bigger, birds (flying ones at least) wouldnīt have arised, and we wouldnīt have airplanes and rockets.
Could the idea of flying have ever occurrred to mankind if birds didnīt exist? What about other technological civilizations? No birds > no rockets > no spaceships > no spacefaring > no close encounter with mankind. What do you think?