On the FBI website you can openly search their UFO files and one report I read stated that a particular set of beings are inter dimensional. Beings that have mastered this and God knows what else would probably not have much interest in the things we have to offer. The inferior can not comprehend the superior. With all of the sightings though out history its probably a safe bet to say they're already here in some form or the other. Its in ancient texts and shaman lore that malice beings have been with us since the beginning. Harnessing are subtle energies for their own sustainment and purpose. While others try and aid with out to much interference in not wanting to disrupt our higher natural cycle of development.