But where is the third eye and what does it do?
My colleague swears by melatonin for alleviating jet lag and recommended I take a dose before departing on a flight across several time zones. The French 17th century philosopher and mathematician Rene Descartes was convinced he had at last found it: the soul. Hindi and Jain women wear a “bindi” (a small red spot on the forehead between their eyes) as a “third eye” to fend off evil (and to look pretty). What do these three statements have to do with each other? Well, we shall see. The organ Descartes regarded as the soul was the “pineal”, also called “epiphysis” – a tiny appendage on the upper side of the brain, located between fore- and midbrain. Though we no longer believe it is the seat of the soul, we still don’t have all the answers regarding its function. In humans and other mammals this small glandular structure appears to be involved in suppressing the maturation of the sex organs, for a pineal tumour or the surgical removal of the structure can result in precocious puberty.
The pineal has also been termed “the internal clock”, for it is known that its hormone, the melatonin, exhibits a 24 hour cycle with peak amounts present at night and light having an inhibitory effect. Jet lag and some forms of depression are thought to be influenced by the pineal and treatment with light is recommended. The structure, however, is also known as “the third eye” for in cold-blooded vertebrates like fish, frogs and reptiles the link between the pineal and light is even closer than in mammals. In many of these lower vertebrates the area of the skull directly above the pineal is less pigmented and allows light to penetrate through a tiny round window. In fish, frogs and reptiles the cells of the pineal in terms of their anatomy, ultrastructure and bio-electrical responsiveness to light are virtually identical to photoreceptors in the retina and the term “third eye” seemed justified – except that research in Sweden has shown that visual cells of the fish pineal develop embryologically well before those of the eye. That suggests the pineal is not the third, but the “first eye” – an eye that is known to be involved in the orientation by polarized light, body colour control, and possibly even magnetorecption in some amphibians and reptiles.
It is still generally accepted that the cells in the mammalian pineal, lacking the photoreceptor characteristics of the cells of the fish, frog and reptilian pineal, represent a more advanced cell type, having acquired an endocrine (= hormonal) function. However, after having examined the pineal of some really archaic not to say primitive fish like lampreys and their larvae, I came to a different conclusion. I see the endocrine-like cell type as the original one, which evolved into the photoreceptor cell type present in fish, frog and reptile pineals. The fact that these photoreceptor cell types reverted back to non-photoreceptor cells, resembling the embryologically first and phylogenetically older cells, I put down to phenomena known as either “neoteny” (in which a juvenile or embryological character is retained into adulthood) or as an “atavism” (the re-appearance of features buried in the genome after they had seemingly disappeared from a species) that was then retained: the reappearance of extra toes in horses, legs in dolphins, teeth in chicks and wings in stick insects are atavism examples – a topic I will definitely write about some time.
What does that leave us with? If the pineal is not the soul, if it is not the third, but the first eye, and if in humans and mammals its cells are not advanced but primitive – well, it leaves us with a lot of “soul-searching”, doesn’t it?
© Dr V.B. Meyer-Rochow and http://www.bioforthebiobuff.wordpress.com, 2017.
Unauthorized use and/or duplication of this material without express and written permission from this site’s author and/or owner is strictly prohibited. Excerpts and links may be used, provided that full and clear credit is given to V.B Meyer-Rochow and http://www.bioforthebiobuff.wordpress.com with appropriate and specific direction to the original content.