Assuming there are aliens on the planet and their presence here isn't interfered with by secret government agencies, demonic legions from the darker side of our religions, or super-powered humans living in the shadows, then it is quite possible extraterrestrial life is in charge. What that degree of control means for the human race is also a factor. Is it everything including money and politics, or just general Do's and Do Not's that regulate our activities?
Long a popular subject of different genres of science fiction favorites, the presence of alien influence is an ever popular one, and it usually exists simply because the human animal is not only a threat to itself, but everything else in the universe. Thus, before enslaving human beings and accidentally triggering their spontaneous evolution into something unstoppable, the aliens sabotage us. Using subtle campaigns, inciting certain events, subject us to disease, or slowing technological progress, their intent is to keep our attentions away from the possibilities of other life forms cohabitating the planet.
Another possibility is that they are shadow helpers, having had a hand in raising human society from infancy by helping build civilizations and languages. There's also the argument that human beings were created by the aliens as slaves to carry out their will or they are so advanced that they only feel the urge to help us along. Considering those options it was nice of them to raise us on such a nice planet, unless water is actually a bad thing on other worlds.
For the sake of argument, there is a possibility that the aliens are of a kind that exist as bacteria or viruses, and study our bodies from the inside as a whole conscious spread along any number of beings, using our immune systems and drug treatments to evolve to a higher level. This would help to explain why new strains of viruses come along so often and do varying degrees of damage. Greater aliens of this type would be able to jump to other hosts by transferring to other objects and directly from person to person in order to explore a broader number of beings, while the weaker ones would depend upon human reproduction or death to advance. The act of the body wearing out may be a miscalculation on their parts as well or malicious intent to thin the populations that are too large.
When it comes to aliens on Earth, there's any number of possibilities. As to which ones are here to help and which are here to control, hopefully governments will one day give us those answers. Until that time, it is necessary to contemplate and wait.