Dr Jacobs - Superior Species
They may have a plan in mind, they may actually interfere with human DNA through breeding, (Gen.6.1-6). The bible and other ancient text show us that the idea of visitors interbreeding with humans is not new. I don't know who "they" are, are "they" all one type of creature like the Jinn or sons of God (fallen angels) or are there numerous types of non-physical entities in our midst? Do they come from other planets or do they live in other dimensions or right under our noses out of sight?
But whoever or whatever "they" are, wherever "they" come from and whatever "they" want, I'm convinced "they" have been around since the beginning of time and they just change their image to keep up with the times.