McKenna suggested that the surreal hallucinatory states experienced by "trippers" might constitute a form of extraterrestrial contact, vastly more intimate than the radio signals anticipated by his mainstream counterparts.
Ludicrous? Perhaps not. Hallucinogenic mushrooms are dispersed as hardy spores capable of traveling incredible distances. McKenna wondered if such spores could have been deliberately wafted to Earth in the remote past, inviting the proposition that many planets conducive to life might have been likewise seeded.
Boldly venturing away from conventional evolutionary narratives, McKenna speculated that homo sapiens might owe its unique cognitive abilities to exposure to psilocybin, a mushroom-derived substance with pronounced neurochemical effects. In McKenna's scenario, the medium is the message: the bizarre worlds encountered by people under the influence of psilocybin are components of an "invisible landscape" with which we share a profound and unacknowledged symbiosis. (McKenna credited the advent of language, among other phenomena, to chemically altered states.)
That our brains harbor receptor sites to specific botanical chemicals indicates a relationship of some complexity, regardless whether the originating organisms are indigenous to Earth or hail from space. If our planet was indeed seeded with fungi, psychedelic experiences might comprise an authentic message, albeit one we have yet to decipher. (Alternatively, McKenna offered the fascinating possibility that hallucinogenic mushrooms themselves could be intelligent in an unrecognized sense, challenging our very definition of the word.)
Recent experiments demonstrate that spores are surprisingly well-suited to the rigors of the interstellar vacuum, vindicating at least a portion of McKenna's proposition. If he was right, then the "aliens" could have already arrived -- a revolutionary notion that pales only when one considers the role they may have played in the development of human consciousness.
This piece originally appeared at aboutSETI.com.