How the Darwinian View of Human "Tails" Leads to Harmful Medical Practices - Evolution News & Views

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How the Darwinian View of Human "Tails" Leads to Harmful Medical Practices

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As we've seen in previous posts (see here, here, here, and here), Darwin-defenders like Karl Giberson have used the rare phenomenon of babies born with supposed "tails" as evidence for common descent. This Darwinian thinking is not merely mistaken but, worse than that, it has led to medical harm. Under the influence of Darwinism, some doctors have viewed so-called "true tails" as benign growths that could simply and expeditiously be excised, calling for no additional examination of the patient. For example, a 1985 paper, "The human tail: a benign stigma," states that "the true human tail is a benign condition not associated with any underlying [spinal] cord malformation."36 Or, as a 1984 paper recommended, a "vestigial tail" can be "easily removed surgically, without residual effects."37 In his recent debate with Stephen Meyer, Dr. Giberson echoed this idea that human tails are found in "otherwise healthy" people.

The papers I just mentioned were written in the mid 1980s, before MRI analyses became widespread and revealed that human tails were commonly associated with other defects and abnormalities. Thus, a more recent paper in Clinical Pediatrics describes the older, "vestigial" view of "true tails":

Attempts have been made to classify tails in human beings as "true" (persistent vestigial) or as "pseudo tail." The true tail is thought to be a benign condition which earlier was thought to have no underlying malformation of the spinal cord or involvement of the neural elements.38
The result of this evolutionary view was that doctors were less likely to suspect, expect, or explore potential neurological problems that might be associated with a tail:
Most human tails have been reported to be located in the lumbar or sacrococcygeal region, and of varying length. As a rule, they were surgically removed, although in many cases the authors failed to discuss the depth of their surgical exploration and whether or not neuroimaging had been undertaken.39
Evolution-based medicine was dangerous in this case because tails are indeed often associated with other underlying problems in development. They are not merely a reversion to a benign ancestral state. The evolution-inspired view has been overturned by medical research finding high levels of defects associated with tails. We discussed this in the previous article, but a little more documentation won't hurt. A 2008 paper in Journal of Pediatric Surgery stated: "In contradiction to a previous report, true vestigial tails are not benign because they may be associated with underlying dysraphic state. About 50% of the cases were associated with either meningocele or spina bifida occulta."40 Such findings now lead doctors to recommend a careful search for other deformities whenever any kind of tail is present. As one paper in Clinical Pediatrics recommends:
[M]ost of the reports in the literature demonstrate such significant associated dysrhaphic states that appropriate neuroimaging should be performed in both ["true" and "pseudo" tail] groups of patients prior to surgical intervention.41
A paper in the journal Minimally Invasive Neurosurgery likewise noted, "The human tail may be related to spinal dysraphism and requires detailed neuroimaging investigation and microsurgery."42 Thus, when a tail is discovered, additional neuroimaging is necessary to determine whether further procedures are needed to remove other tail-associated defects that could lead to neurological problems, if left untreated.

Another paper recounted the dangers of leaving these defects untreated:

This [high incidence of defects associated with tails] is the most clinically significant finding, since removal of lipomas and spinal cord untethering can prevent the development of irreversible neurologic deficits of the lower extremities, bowel and bladder. ... Removal of the tail is indicated for cosmetic purposes only, but removal of a spinal lipoma and untethering of the spinal cord are necessary to prevent the development of irreversible neurologic deficits.43
A paper in Journal of Child Neurology likewise elaborates the dangers of failing to look for these other defects, since the human tail "can be associated with an underlying spinal lesion that, if not recognized early, can lead to permanent neurologic disabilities."44 If you treat the tail as a vestigial throwback in "otherwise healthy" babies, then you won't do the detailed examinations necessary to find these problems and properly treat them.

Unfortunately, some experts wanted so badly to see tails as benign that they misguidedly defined "true tails" and "pseudotails" in such a way that if an abnormality were found, then by definition the tail could not be a "true" tail. One paper in British Journal of Plastic Surgery explains:

To state that a caudal appendage is not a true tail simply because it is associated with spina bifida or meningocele, or with neoplastic or ectopic histological elements, is probably inaccurate.45
This Darwinian view also ignores the fact that both "true tails" and "pseudotails" can be associated with abnormalities, a fact that could blur or negate such distinctions between the two:
Although more than 10 years have passed, the 'human tail' is still ill-defined. It has been classified as either a true (persistent vestigial) tail or a pseudotail. A true tail is thought by some authors to be a benign condition not associated with any underlying spinal cord malformation. Other researchers have emphasized that the classification of each caudal appendage into true tail or pseudotail remains obscure and the distinction on clinical examination is dubious at best.46
Because true tails are associated with defects, including abnormalities of the spinal cord, these authors reject the idea that there is a clinically important distinction between the true tail and the pseudotail: both can be associated with problems and need to be removed with great care. Thus, one. A paper in the Journal of Pediatric Surgery agrees:
The distinction between the true tail and pseudotail on clinical examination is almost always dubious, and despite a normal neurological examination, normal plain x-ray of spine, and clinical classification of true tail, subfascial exploration may show tethered cord or lipomeningomyelocele as what occurred in our case. Hence, ignoring the type of tail, each individual case needs comprehensive preoperative investigation, and surgical exploration of the intraspinal content should be done microsurgically to avoid any damage or neurological deficit.47
Another paper likewise concludes that the "true tail" versus "pseudotail" distinction derives from evolutionary theory, and is clinically unhelpful:
The terms "true tail" and "pseudotail" have no clinical significance and should probably be abandoned, except possibly by embryologists. Lu et al. have proposed a more practical description using MR, and simply divide tailed patients into those with or those without associated tethering of the spinal cord. ... Conclusions regarding the evolutionary significance of the tail and distinctions between true tail and pseudotail are clinically unimportant and should be abandoned. 48
In sum, it was overcoming Darwinian thinking that led to better medicine. But this raises additional questions. If both pseudotails and true tails are associated with many of the same developmental defects, could that suggest they have similar causes? If so, where does that leave the view, articulated by Karl Giberson and others, of the tail as a vestigial evolutionary holdover?

References Cited:

[36.] Roberto Spiegelmann, Edgardo Schinder, Mordejai Mintz, and Alexander Blakstein, "The human tail: a benign stigma," Journal of Neurosurgery, 63: 461-462 (1985) (emphasis added).

[37.] Anh H. Dao, Martin G. Netsky, "Human Tails and Pseudotails," Human Pathology, 15(5): 449-453 [May 1984).

[38.] Hector E. James and Timothy G. Canty, "Human Tails and Associated Spinal Anomalies," Clinical Pediatrics, 34: 286-288 (1995) (emphases added).

[39.] Hector E. James and Timothy G. Canty, "Human Tails and Associated Spinal Anomalies," Clinical Pediatrics, 34: 286-288 (1995) (emphasis added).

[40.] Deepak Kumar Singha, Basant Kumarb, V.D. Sinhaa, and H.R. Bagariaa, "The human tail: rare lesion with occult spinal dysraphism--a case report," Journal of Pediatric Surgery, 43: E41-E43 (2008) (emphasis added).

[41.] Hector E. James and Timothy G. Canty, "Human Tails and Associated Spinal Anomalies," Clinical Pediatrics, 34: 286-288 (1995) (emphases added).

[42.] E. Gonul, Y Izci, O. Onguru, E. Timurkaynak, N. Seber, "The Human Tail Associated with Intraspinal Lipoma Case Report," Minimally Invasive Neurosurgery, 43: 215-218 (2000).

[43.] Daniel J. Donovan Robert C. Pedersen, "Human Tail with Noncontiguous Intraspinal Lipoma and Spinal Cord Tethering: Case Report and Embryologic Discussion," Pediatric Neurosurgery, 41:35-40 (2005) (emphases added).

[44.] Dipti Kumar and Akshay Kapoor, "Human Tail: Nature's Aberration," Journal of Child Neurology, 27: 924 (2012) (emphasis added).

[45.] Abraham M. Baruchin, Dan Mahler, Dan J. Hauben, and Lior Rosenberg, "The human caudal appendage (human tail)," British Journal of Plastic Surgery, 36: 120-123 (1983).

[46.] A.M. Baruchin, "Human tail," British Journal of Plastic Surgery, 48: 114-115 (1995).

[47.] Deepak Kumar Singha, Basant Kumarb, V.D. Sinhaa, and H.R. Bagariaa, "The human tail: rare lesion with occult spinal dysraphism--a case report," Journal of Pediatric Surgery, 43: E41-E43 (2008) (emphases added).

[48.] Daniel J. Donovan Robert C. Pedersen, "Human Tail with Noncontiguous Intraspinal Lipoma and Spinal Cord Tethering: Case Report and Embryologic Discussion," Pediatric Neurosurgery, 41:35-40 (2005).

Photo source: Steve Harris/Flickr.