As with Yeti's I believe they exist.

Dont see how people could be so naive to believe we are the only lifeform to exist in this universe. Considering it's ever increasing, and the amount of galaxies out there, are we really to believe we are the only lifeform

Anyway, our existence on this planet is only an experiment by another lifeform. We were put here to see how the human race would evolve, and eventually destroy the planet they put us on. Every now and then they pop down to check on us and perform experiments on us. Simples