After reviewing the article that was written by Benny Shanon in 2008, I would like to say that it was a very informative read. I am currently reading the book "Failed God" by John A. Rush where he talks about Christianity, Judaism, and Isam to be started with the use of entheogens. Interesting enough Shanon's work with this article pretty much sums up all of Rush's work in a few pages. Shanon also goes into what plants may be the tree of knowledge and focuses on the "newly" researched Acacia Tree as being the source of the large amounts of DMT. Though recently we have been able to determine how much DMT is located in the Acacia Confusa, it still has had the focus as a high yielding DMT source and involved in religious practices for thousands of years.
Over all, anyone that is interested in learning some good hypotheses on the use of hallucinogens in ancient religious practices, you should read Shanon's article.
read the article: here