We as humans conduct many experimental projects specially about life. We create an environment for viruses, watch their behaviour to understand them. There could be another super earth, where there were much more evolved super humans, whose lifespan is few thousand years and live in some other galaxy, They chose our galaxy, created a living environment around earth and started an experiment with plants, birds, animals and us. Maybe sometime later, this experiment was abandoned due to lack of interest or budget constraints and here we are on a never-ending journey chugging along in a self running mode. logically quite possible.