A term coined by Terence McKenna referring to the modern cultural mode that recapitulates patterns of human behavior from prehistory. As the following quote from Alien Dreamtime elaborates, the Archaic Revival includes activities like ecstatic dance and music (rave culture), ingestion of entheogens (psychedelic culture), even group mind behavior (the internet).
History is ending, because the dominator culture has led the human species into a blind alley. And as the inevitable chaostrophe approaches, people look for metaphors and answers. Every time a culture gets into trouble, it casts itself back into the past looking for the last sane moment it ever knew. And the last sane moment we ever knew was on the plains of Africa, 15,000 years ago, rocked in cradle of the great horned mushroom goddess before history. Before standing armies, before slavery and property, before warfare and phonetic alphabets and monotheism. Before, before, before. And this is where the future is taking us. Because the secret faith of the 20th century is not modernism. The secret faith of the 20th century is nostalgia for the archaic, nostalgia for the Paleolithic, and that gives us body piercing, abstract expressionism, surrealism, jazz, rock and roll, and Catastrophe Theory. The 20th century mind is nostalgic for the paradise that once existed on the mushroom-dotted plains of Africa, where the plant-human symbiosis occurred that pulled us out of the animal body and into the tool-using, culture-making, imagination-exploring creature that we are.

- from Alien Dreamtime

The Archaic Revival is also a book by Terence McKenna, a collection of essays and interviews detailing his ideas on topics ranging from UFO to DMT.