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Human tails?

‘Atavistic tails’ and evolution

by and Carl Wieland

iStockphoto baby-sleeping

A persistent argument for evolution is the idea of supposed atavistic organs. These are thought to be ‘throwbacks’ to a believed evolutionary ancestral state. This is allegedly caused by genetic information within the DNA for that ancestral trait which is somehow (e.g. by mutation) ‘uncovered’ or able to express itself. Whereas it had previously been ‘covered’ or repressed (‘switched off’), now it is ‘switched on’.

This is related to (but not the same as) the issue of so-called ‘vestigial’ organs, which are supposed to be useless or degenerate organs that are a ‘leftover’ from our evolutionary past. A prime example of this in humans used to be the appendix, now known to have definite function.

Serious medical researchers now refer to this sort of structure as “a disturbance in the development of the embryo but not a regression in the evolutionary process.” [from Paediatric Neurology]

Creationists have long debunked vestigial claims for human organs and features such as the appendix, tonsils, coccyx, male nipples, body hair, etc. Even many evolutionists have abandoned these weak and tired arguments. Some seek to redefine or at least nuance the term to try to evade the force of these refutations,1 but close scrutiny continues to show the weakness of the argument. More modern versions of these ‘vestigial’ claims (such as the failed ‘Junk DNA’ idea) constantly arise as older arguments fall off the evolutionary bandwagon.

This never-say-die enthusiasm is because any useless or ‘left-over’ organs would be seen as ‘smoking gun evidence’ of our long evolutionary march from earlier organisms to our present form. Why else, they say, would we carry genetic information for organs and features that serve no purpose today? Much the same argument applies, of course, if one could point to atavisms, or spontaneously appearing ‘throwbacks’ to an organ that an ancestor had, but which does not appear in most ‘normal’ humans.

Humans with tails?

A popular example of ‘atavism’ these days is the claim that humans are sometimes born with fully functioning tails. Just such a claim was made by the professing (but questionable) Christian Karl Giberson (a major contributor to the theistic evolutionary organization Biologos and author of the book Saving Darwin; How to be a Christian and Believe in Evolution) during a debate with Intelligent Design proponent Stephen Meyer.

Writing about this aspect of the debate afterwards, Giberson said:

“Why does the human genome contain instructions for the production of features we don’t use? The scientific explanation is that we inherited these instructions from our tailed ancestors but the instructions for producing them have been shut off in our genomes, which is why Shallow Hal2 is the only person most people know who has a tail. Sometimes the ‘ignore these genes’ message gets lost in fetal development, however, and babies are born with perfectly formed, even functional tails.”3

During his debate Giberson actually showed a photo of a human baby with a tail attached to verify his claim.4 Embarrassingly for him, it turned out to be a photoshopped image apparently obtained from the satirical website cracked.com (a ‘vestigial remnant’ of the knock-off of Mad magazine)5 rather than a real medical example! Giberson has since apologized but it is hardly a shining example of due diligence for a Ph.D. scientist, and a good warning for those who blindly accept such evolutionary ‘evidences’ without thoroughly examining their validity.6

Prominent atheistic evolutionist and biologist Jerry Coyne makes similar claims in his book Why evolution is true. He says:

“Rarely … a baby is born with a tail projecting from the base of its spine. The tails vary tremendously … some … contain vertebrae … Fortunately, these awkward protrusions are easily removed by surgeons.”7

So the claim by many evolutionists is that sometimes human babies are born with “perfectly formed, even functional tails” which are obvious ‘throwbacks’ to the tailed condition of their evolutionary ancestors.

As alluded to earlier, they claim that the ‘vestigial’ genes for these tails remain encoded in the DNA of all humans, and that the tails form when these normally dormant genes are accidentally reactivated. Further proof of this idea is said to be the fact that what is alleged to be a ‘tail’ can be seen forming in every human embryo (although this ‘tail’ disappears during normal development).

They also state that people with these tails at birth are often perfectly normal and healthy and the tails are (as Coyne says) ‘easily removed’ (presumably meant to reinforce the idea that these evolutionary atavisms aren’t pathological, i.e. ‘abnormalities’ in the sense of causing disease or disability).

Do people have tails?

Humans are sometimes born with various types of bulbous or tubular growths, from a number of different types of causes. Where these are on their lower backs, though medically termed ‘caudal appendages’, they are commonly referred to as ‘human tails’.8 An online image search using the search phrase ‘human tails’ reveals many (sometimes disturbing) images of people with this sort of condition.

The most popular story lay people have been exposed to regarding this is probably that of Arshid Ali Khan, a teenager from Punjab in India. A ‘human tail’ search online is virtually guaranteed to find news reports, videos and images regarding this young man. He has been hailed by some as a reincarnation of the Hindu monkey god Hanuman because of the 18-cm (7-inch) tail he has. Unfortunately, like most people born with ‘tails’, he has associated medical challenges. He cannot walk because of partial paralysis and must use a wheelchair. The UK’s Daily Mail has reported that doctors are considering removing the appendage, as even though Arshid’s condition has not been formally diagnosed, they:

“… believe his tail and partial paralysis could be a sign that he has a form of spina bifida called meningocele. This develops when membranes poke through a hole between the vertebrae in the back.”9

What are these ‘tails’?

There are, broadly speaking, two types of these appendages, which may vary from a few centimetres to well over 10 centimetres long. In medical literature some are referred to as ‘true tails’ (which contain muscle, can move and are located extending from the coccyx) and others are termed ‘pseudo tails’ (which are generally flaccid and can be located in a variety of places). This terminology itself (based on evolutionary assumptions) is one of the challenges for creationists arguing against evolutionists about this claim. Someone investigating this debate can find scientific papers where doctors and scientists use the term ‘human tails’, so many people look no further and cite them as experts confirming the evolutionary argument.

The problem is that the term ‘tail’ is used more descriptively than scientifically. If someone is born with a tubular growth extending from their shoulder or arm10 it is not usually referred to as a tail because it isn’t situated in the area in which most people would expect to see a tail on a creature. But when one appears on the lower back or buttocks it is easy to see why the term is used. The fact that some of these ‘tails’ can appear other than where tails on creatures would normally be is a good argument against them truly being vestigial growths, but rather pathological, i.e., abnormalities of normal human development unrelated to any ‘ancestral genes’.

As one researcher from Duke University Medical Center (Durham, N.C) stated:

“One of the earliest etiological [causal] explanations for the ‘human tail’ was that it was a remnant of the embryologic tail seen during gestation. There are several problems with this theory, the most obvious being that these occur in locations other than the embryologic sacrococcygeal region.”10

Even the names ‘true tail’ and ‘pseudo tail’ are misleading, because the causes of each of these deformities are now thought to be related.

“Caudal appendages or human tails were divided by Dao and Netsky into true tails, which contain muscle and are movable, and pseudotails, which do not move. However, this is now considered arbitrary and without clinical significance as both kinds are derived from notocordal remnants and the etiology [= cause] of both is probably similar.”11

Harmless leftovers?

Modern doctors familiar with this sort of condition seem unanimous in their description of human tails as being the result of birth defects. Like the example of Arshid Ali Khan, almost all of those with these caudal appendages have related potentially serious medical conditions. Of the anomalies associated with people that have ‘tails’, the most common are spinal dysraphism, meningocele, spina bifida (on its own), and tethered spinal cord, with many others also being reported.12

Human ‘tails’, although extremely rare, have been known about for a long time. It has only been fairly recently though that techniques like CT (computerized tomography) and MRI (magnetic resonance imaging) scans have been available, and some of the conditions associated with these caudal appendages can only be properly diagnosed and assessed using such equipment.

A case report published in 2010 said the following;

“A human tail is a rare congenital anomaly with a prominent lesion from the lumbosacrococcygeal region. Many authors saw this curious and rare condition to be evidence of man’s descent from or relation to other animals … Advanced imaging technology in recent decades has allowed a more thorough investigation of these patients and better defined their association with spinal dysraphism and tethered spinal cord.”13

A 2008 report in the Journal of Perinatology stated:

“The most important feature of caudal appendages is the possibility of associated spinal dysraphism, which needs to be treated to prevent the development of neurologic symptoms. Therefore, caudal appendages require meticulous imaging and neurological evaluation to insure that appropriate surgery is performed to prevent progressive neurologic symptoms.”14

However, papers written ‘pre-MRI’, so to speak, made claims like this (not speaking of lipomata, see Fatty Folly):

“(a) vestigial tail” can be “easily removed surgically, without residual effects.”15

“The true human tail is a benign condition not associated with any underlying (spinal) cord malformation.”16

So older commentory on this condition may have seriously underestimated the associated medical problems of patients with ‘tails’ because of a lack of equipment, and/or the false Darwinian concept of ‘atavistic organs’ they learned from their text books.

Whether such a ‘tail’ has muscle (which makes it movable) or not, due to the frequent association of a suite of abnormalities, serious medical researchers now refer to this sort of structure as “a disturbance in the development of the embryo but not a regression in the evolutionary process.”17

Fatty folly

On occasions, an assumed ‘tail’ turns out to be a simple fatty tumour, known as a lipoma. Lipomas are common and can occur just about anywhere there is fatty tissue, commonly forming just under the skin. They can often develop and grow in an adult, too. On the many occasions that such a tumour happened to appear in any other region of the body, it would never be suggested that it was a tail, even if it were somewhat elongated. Unlike the ‘human tails’ discussed by medical researchers, a lipoma can indeed be very easily removed, even by someone with very limited surgical experience. And upon such removal, the diagnosis will be obvious, which is that it has nothing to do with tails, atavistic or otherwise.

The tale of the human embyronic ‘tail’

Nonetheless, such a powerful and graphic idea as a ‘human tail’ dies hard, and (especially when bolstered with faked and photoshopped images and video footage) remains popular on the internet. Reinforcing it is the idea that all human embryos have ‘tails’ at one stage. Many believe that the genes responsible for this ‘embryonic tail’ are the ones that when ‘not switched off’, are the cause of the ‘human tails’ discussed here.

Giberson says;

“… we inherited these instructions [for tails] from our tailed ancestors but the instructions for producing them have been shut off in our genomes…”18
“Sometimes the ‘ignore these genes’ message gets lost in fetal development, however, and babies are born with perfectly formed, even functional tails.”18

He also expresses these ideas in his book Saving Darwin where he writes (emphasis added):

“Two-month-old embryos of chicken, pigs, fish, and humans look similar. They all have gills, webbed hands and feet, and tails. In a few weeks these formations disappear from the human embryo.” 19
  • Gills?

The idea that the human embryo contains gills has long been discredited. Even a standard embryology text20 said as far back as 1981 that the grooves often called branchial (gill) clefts are now properly called pharyngeal, not branchial, because “in the human embryo real gills—branchia—are never formed.”21

  • Webbed feet?

Similarly for the idea of ‘webbed feet’. Human hands and feet are unique from the beginning, and of course we are not supposed to have descended from any duck-like ancestor anyway. The human digits form from an embryonic plate (See Refuting Evolution 2, chapter 6) in which apoptosis—programmed cell ‘death’—between the areas destined to become digits then leaves those behind. Rarely, the digits are incompletely separated at birth, which might have given traction to the ‘webbed’ myth.

  • Tail?

The idea that all human embryos have a ‘tail’ is similarly false if by that is meant anything to do with a tailed ancestor. It comes from the fact that during the fourth or fifth week of the normal process of development, all humans develop aposterior extension of the embryo’s developing musculoskeletal structure beyond the anus that helps unfold the human body plan and nervous system. This is, however, not because of some vestigial ‘tail DNA’; it is a critical stage of programmed human embryonic development as the notochord and neural tubes extend throughout most of this tail-shaped structure.

This structure, only very superficially like a tail, acts as a type of template or scaffolding which induces or guides the formation of other structures at precise times during later development (for example the notochord acts as a template for cells that develop into vertebrae). Once those developments are complete genetic programming ensures the removal of the original structure as it is no longer needed. And this is not unique to just this posterior extension; many such structures form and are reabsorbed during normal human development. The Annals of Anatomy (though unfortunately perpetuating the convention of calling it a ‘tail’) describes it this way:

“During normal human development a number of transient structures form and subsequently regress completely. One of the most prominent structures that regress during development is the human tail … Initially, the human tail is composed of tail bud mesenchyme which differentiates into caudal somites, secondary neural tube, notochord and tail gut.”22

An analogy would be like a stone mason making an archway. Because the stones of an arch will not stand by themselves until the keystone is placed to complete it, masons build a ‘buck’ (a wooden scaffold in the shape of the arch) underneath it so that it will support the stones as the arch is being built. Upon completion the buck is removed and the completed archway is self-supporting. Unless you had watched the arch being built you may never have known the scaffold was ever there. And it typifies forethought and design, not some haphazardly thrown-together accumulation of leftovers.

Fully functioning tails?

Analyzing the declaration that humans are sometimes born with ‘fully functioning’ tails can be better achieved by defining what a real tail is, what the functions of tails are, and the structure required for that function, then comparing them to so-called ‘human tails’. Remember, the argument about ‘fully functioning’ is not whether humans have ever been born with a growth where a tail might be (if we had been designed with tails). Nor even whether a protrusion caused by developmental abnormality ever contains muscle (which if connected to nerves will contract and thus cause the protrusion to move). It is whether humans ever have actual tails comparable to animal tails or not (whether in embryonic form or when born).

Thus, the claim that humans are sometimes born with ‘fully functioning’ tails is misleading and false.

Animal tails have fully developed structural vertebrae continuing past the rear hips with appropriately attached muscles, nerves activating these muscles with the appropriate neural pathways for the control of the tail (all the way to and in the brain) and other needed soft tissues present in anatomically appropriate relationship with all these.

The tails of animals, under the control of the respective creatures, are used for the following: prehensile grasping, brushing insects away, as a decoy for defence (like when lizards voluntarily detach their tails), communication (like a dog wagging its tail to show it is happy, or a cat slashing its tail to show it is upset), keeping warm (like a husky laying in a circle and covering its nose), and probably most importantly, for balance when walking and running.

Despite the impression one gains, no so-called ‘true tail’ (remember, these have muscle) in humans has ever been found to contain bone or cartilage.23,24 And even though ‘pseudo-tails’ have been found to contain bone, they don’t contain vertebrae (Coyne’s statement that some human tails have vertebrae appears to be false from all accounts we have been able to assess). So all these caudal appendages do not closely resemble at all any real animal tail structurally. And no humans born with such an abnormality are able to use their caudal appendage for any of the functions above. Thus, the claim that humans are sometimes born with ‘fully functioning’ tails is misleading and false.

Physician and surgeon Dr. Michael Egnor (Vice-Chairman, Department of Neurological Surgery, and Director, Pediatric Neurosurgery, at State University of New York at Stony Brook) who has actual surgical experience with this type of condition stated the following about ‘human tails’:

None of them—and none of the reports in the literature that I know of—are actual tails.—Michael Egnor (Director, Pediatric Neurosurgery, State University of New York).
“None of them—and none of the reports in the literature that I know of—are actual tails. A tail has vertebrae, is a continuation of the coccyx, has developed muscles, nerves and other soft tissues, etc. The appendages described in the literature, and all of the appendages on which I have operated, are dysmorphic mesenchymal tissue, often epithelialized exophytic dermal sinus tracts, that bear a superficial resemblance to a ‘tail’. None have the structure of a tail, even in rudimentary form, and none of the ones I have operated on were attached to the coccyx in the way that a tail is.”25

For those unfamiliar with medical terminology that means that these so-called human tails are an abnormality consisting of a specific group of malformed cells (typically those capable of developing into connective tissues) from the middle germ layer of an embryo that form a lesion protruding outward from the skin forming a ‘tail-like’ growth. It is this middle germ cell layer, by the way, the mesoderm, which normally develops into structures that include muscle, so the presence of muscle in the occasional one of these is no surprise.

Summary and conclusion

  1. The human embryo never has a ‘tail’ at any stage.
  2. Developmental abnormalities can rarely cause caudal appendages which have been loosely termed ‘tails’.
  3. These can be of varying types, and sometimes contain innervated muscle, causing them to be ‘movable’.
  4. Though this has unfortunately led to the term ‘true tails’, no babies are ever born with anything that could be remotely called a true tail, structurally and functionally.
  5. Medical researchers and clinicians that are faced with these rare occurrences are increasingly stating the obvious (whether or not they believe in evolution) that none of them are tails. Rather, they affirm their status as various types of birth defects, unrelated to any ‘animal ancestry’.
  6. People with these caudal appendage defects most often suffer from a variety of potentially serious medical conditions (and most of the appendages are not ‘easily removed’ as vocal evolutionists claim).
  7. These defects clearly provide no support for the claim that humans have vestigial genes for tails encoded in our DNA.

Once again a Darwinian myth, in this case ‘atavistic’ or ‘throwback’ organs, has been shown to be scientifically false. Try as hard as they might, they still can’t make a monkey out of us.

Published: 30 April 2015

References and notes

  1. This refers to the claim that an organ does not have to be totally useless to be considered vestigial. I.e. it may have degenerated from its original function and then later developed a different one, i.e. been ‘co-opted’. For example, the wings of flightless birds (which creationists also often think are the result of loss of function mutations) may be used for a balancing function when running. Return to text.
  2. A crude 2001 movie that features a prominent character with a supposed ‘vestigial tail’. Return to text.
  3. Giberson, K., Science Wars, My Debate With an ‘Intelligent Design’ Theorist, The Daily Beast, April 21 2014, thedailybeast.com. Return to text.
  4. This image can be seen at www.sciencephoto.com/media/89784/view. Return to text.
  5. Klinghoffer, D., Karl Giberson Apologizes for Photoshopped Image of Tailed Baby, evolutionnews.org, 6 June 2014. Return to text.
  6. The internet contains many doctored or ‘tricked’ images, both still and video, claiming to be real, and these include some of ‘functioning tails’. Unfortunately, some fraudsters also take in many Christians with fake ‘archaeological’ and similar claims purportedly supporting the Bible, e.g. the notorious ‘giant pre-Flood human skeleton’ photos. See Arguments we think creationists should not use. Return to text.
  7. Coyne, J. A., Why Evolution Is True, OUP Oxford, 2009, p.70. Return to text.
  8. Gaskill, S.J. and Marlin, A.E., Neuroectodermal appendages: the human tail explained, Pediatr Neurosci 15(2):95–99, 1989; US National Library of Medicine, National Institutes of Health, Pub Med.gov, Page 97,ncbi.nlm.nih.gov. Return to text.
  9. Indian teenager is worshipped because he has a seven inch TAIL—but may need it removed as he’s unable to walk, The Daily Mail, 17 June 2014, dailymail.co.uk. Return to text.
  10. Gaskill & Marlin, op. cit., p. 97. Return to text.
  11. Herman, T.E. and Siegel M.J., Human tail-caudal appendage: tethered cord, Journal of Perinatology 28: 518–519, 2008. Return to text.
  12. Lu, F.L., Wang, P.J., Teng R.J., Tsou Yau, K.I., Frank L. Lu, Pen-Jung Wang, Ru-Jeng Teng, and Kuo-Inn Tsou Yau, The Human Tail, Pediatric Neurology 19(3), 1998. Return to text.
  13. Chunquan C., Surgical treatment of a patient with human tail and multiple abnormalities of the spinal cord and column, Department of Pediatric Neurosurgery, General Hospital of Tianjin Medical University, no. 154, China, Research Gate,researchgate.net. Return to text.
  14. Herman, T.E. and Siegel, M.J., Human tail–caudal appendage: tethered cord, Journal of Perinatology 28:518–519, 2008 | doi:10.1038/jp.2008.39. Return to text.
  15. Dao, A.H. and Netsky M.G., Human Tails and Pseudotails, Human Pathology 15(5):449–453, 1984. Return to text.
  16. Spiegelmann, R., Schinder, E., Mintz, M, and Blakstein, A., The human tail: a benign stigma, Journal of Neurosurgery 63(3):461–462, 1985. Return to text.
  17. Lu, F.L. et al., op cit. Return to text.
  18. Giberson, K., Science Wars, My Debate With an ‘Intelligent Design’ Theorist, The Daily Beast, 21 April 2014, thedailybeast.com Return to text.
  19. Giberson, K., Saving Darwin: How to be a Christian and Believe in Evolution, HarperOne, New York, 2008, p. 200. Return to text.
  20. Langman, J., Medical Embryology, 4th edition, Williams & Wilkins, Baltimore, 1981. Return to text.
  21. There are no gill slits, either, in human embryos—the same text referenced above says (on p. 268) that the associated pouches “do not establish an open communication with the external clefts”. Return to text.
  22. Morphological diversity of dying cells during regression of the human tail, Annals of Anatomy 183:217–222, 2001, sciencedirect.com. Return to text.
  23. Dao, A.H, Netsky, M.G., Human tails and pseudotails, Human Pathology 15(5):449–53, 1984; US National Library of Medicine, National Institutes of Health, PubMed.gov, ncbi.nlm.nih.gov. Return to text.
  24. Spiegelmann, R., et al, op.cit. Return to text.
  25. Egnor, M., The Myth of Human ‘Tails’: A Physician and Surgeon’s Perspective, Evolution News and Views, May 23, 2014, evolutionnews.org. Return to text.