ng caudal vertebrae or an increased number of vertebrae in the medical literature, and there is no zoological precedent for a vertebral tail without caudal vertebrae."6
- Finally, an article in Human Pathology explains: "In humans a true tail, is vestigial, however, and never contains vertebrae. ... Bona-fide cases of human tails containing bone have not been documented."7
But what about "pseudotails" -- can't they contain bone? Yes, sometimes they can, but pseudotails don't contain vertebrae (as all other mammalian tails do), and they're not located at the base of the coccyx, where a "true tail" ought to be -- they are found in various other places along the lower back, and may even be off to the side from the backbone. Moreover, "pseudotails" are often found associated with other types of defects, and are obvious deformations, as multiple papers have recognized:
- "The pseudotail is an anomalous prolongation of the coccygeal vertebra, lipoma, teratoma, chondrodystrophy, or parasitic fetus."8
- "The pseudotail has no embryological relationship to human tail development, but is any variable abnormal caudal tail-like structure or protrusion."9
- "Pseudotail has no relationship to human tail development; it is a tissue that has been accidentally located in the lumbrosacrococcygeal area."10
- "Pseudotails are varied lesions with only a superficial resemblance to the true vestigial tail. The most common cause of a pseudotail is a prolongation of the coccygeal vertebra"11
- "The pseudotail is often short, stump-like, and occasionally bulging. It may be composed of teratomatous elements, adipose tissue, or cartilage."12
Nonetheless, it's quite reasonable to wonder why humans have these things called "true tails" -- which have a non-trivial superficial resemblance to a real tail, despite their significant differences -- in the first place? And intriguingly, why are humans occasionally found with "pseudotails" -- growths that also superficially resemble tails, but are clearly deformations, defects, and abnormalities? Could the fact that humans have obviously deformed pseudotails near the same location as "true tails" provide a hint about what causes the formation of "true tails"? Is the distinction between a "true" and "pseudo" tail medically sound?
To help us begin to answer these questions, in my next post I will assess Giberson's claim that tails result from the simple turning on of vestigial genes.
[1.] Roberto Spiegelmann, Edgardo Schinder, Mordejai Mintz, and Alexander Blakstein, "The human tail: a benign stigma," Journal of Neurosurgery, 63: 461-462 (1985).
[2.] Roberto Spiegelmann, Edgardo Schinder, Mordejai Mintz, and Alexander Blakstein, "The human tail: a benign stigma," Journal of Neurosurgery, 63: 461-462 (1985).
[3.] Surasak Puvabanditsin, Eugene Garrow, Sharada Gowda, Meera Joshi-Kale, and Rajeev Mehta, "A Gelatinous Human Tail With Lipomyelocele: Case Report," Journal of Child Neurology, 28(1) 124-127 (2013) (emphases added). See also Biswanath Mukhopadhyay, Ram M. Shukla, Madhumita Mukhopadhyay, Kartik C. Mandal, Pankaj Haldar, and Abhijit Benare, "Spectrum of human tails: A report of six cases," Journal of the Indian Association of Pediatric Surgery, 17(1): 23-25 (Jan-Mar, 2012).
[4.] Allan Joel Belzberg, Stanley Terence Myles, and Cynthia Lucy Trevenen, "The Human Tail and Spinal Dysraphism," Journal of Pediatric Surgery, 26: 1243-1245 (October, 1991) (emphasis added).
[5.] S.P.S. Chauhan, N.N. Gopal, Mohit Jain, and Anurag Gupta, "Human tail with spina bifida," British Journal of Neurosurgery, 23(6): 634-635 (December 2009) (emphasis added).
[6.] Fred Ledley, "Evolution and the Human Tail," The New England Journal of Medicine, 306 (20): 1212-1215 (May 20, 1982) (emphases added).
[7.] Anh H. Dao, Martin G. Netsky, "Human Tails and Pseudotails," Human Pathology, 15(5): 449-453 [May 1984) (emphasis added).
[8.] Surasak Puvabanditsin, Eugene Garrow, Sharada Gowda, Meera Joshi-Kale, and Rajeev Mehta, "A Gelatinous Human Tail With Lipomyelocele: Case Report," Journal of Child Neurology, 28(1) 124-127 (2013).
[9.] S