In Theosophy it is related to the pineal gland.[10] According to this belief, humans had in far ancient times an actual third eye in the back of the head with a physical and spiritual function. Over time, as humans evolved, this eye atrophied and sunk into what today is known as the pineal gland.[10] Dr. Rick Strassman has hypothesized that the pineal gland, which maintains light sensitivity, is responsible for the production and release of DMT (dimethyltryptamine), an entheogen which he believes possibly could be excreted in large quantities at the moments of birth and death.[11]