The universe is far too vast to not contain forms of life foreign to humans. We cant even venture outside our own galaxy.
Now, as far as ET's visiting/monitoring Earth..maybe. There is ample evidence to show it. I find quite interesting that the Egyptians could build pyramids to such a high standard, only using manpower. I think they had help. After all, they did depict objects that looks like flying saucers, planes and UFO in hieroglyphs. Not to mention government conspiracies (Roswald), countless video footage of unexplainable objects, and many claims of personal encounters. We just need the nail in the coffin.
This is branching off quite a bit but i'll throw it in there. Some believe that consciousness is recieved, from what? Who knows. Some also believe that humans have been genetically modified, either by our own species or by another. We only have the ability to use a small portion of our brain. With that small amount, we think we're intelligent. Imagine what we may have been, or could be.
Our universe is infinite and ever expanding. We are but a grain of sand, literally. We are nothing. The possibilities are endless, and I see zero problem with speculating. As long as it is within reason and is rational of course. Maybe thats a contradiction considering what we're speculating. I'll leave with this quote, nice thread:
"Two possibilities exist. Either we are alone, or we are not. Both are equally terrifying."
-Unknown