I've been attempting to reconcile the "visionary" nature of encounters with nonhumans described by the likes of Terence McKenna with the decidedly physical episodes recounted by close-encounter witnesses. Must the "alien contact" experience be exclusively "real" or hallucinatory? Maybe not.
The psychedelic realm has the visual flexibility of a multimedia installation or high-bandwidth website, forcing me to consider that it's actually designed as a communications system: a sort of neurochemically derived "chatroom" populated by all manner of colorful "avatars."
It's conceivable that "trippers" can access this interzone, even if inadvertently. The beings seen -- described similarly in UFO and drug narratives -- might be the equivalent of neuropharmacologists and system operators. (Online environments like Second Life, while fanciful, abide by many of the conceits and laws that govern the real world, if only for the sake of convenience. It's likely that an alien intelligence versed in nonlocal communication would apply similar reasoning when constructing a virtual environment.)
If access to the shamanic realm hinges on the brain's production of DMT, as argued by Richard Strassman, then the "aliens" may be attempting to promote organic DMT production through germ-line engineering.