Renowned enthnopharmacologist, Dr. Dennis McKenna, talks about the pharmacology and origins of ayahuasca. The ayahuasca tea is made from combining the banisteriopsis caapi vine and the leaves from any of a number of other plants, usually Psychotria viridis (chacruna) or or Diplopterys cabrerana (chaliponga). When Amazonian curanderos are asked how they knew to put these two plants together to make ayahuasca, they reply, "The plants told us how to do this."
This clip is taken from bonus materials included in the DVD. (Reposted Nov 8/10 with improved audio tracking.)