Well one of the theories to human existence is that we were genetically engineered by aliens; that is, ape dna mixed with their own.

Ancient Sumerian texts allude to that, and seeing modern docos of precision placed ancient stone blocks that we cannot move with today's technology, or sophisticated mining shafts that were 50k years old, the stuff done in south america like open cut stone mountains, etc do raise an eyebrow.

I haven't seen aliens nor ufos but i have an open mind.. billions of stars in this multiverse and all it takes is just one exoplanet like ours to sustain life and with more technologically advanced inhabitants than us to be curious enough and explore.