Are Humans Ever Born with "Perfectly Formed" Tails?
In The Descent of Man, Charles Darwin cited the tailbone (coccyx) as a supposed vestigial feature revealing our descent from tailed ancestors. He wrote: "In certain rare and anomalous cases it [the coccyx] has been known... to form a small external rudiment of a tail." Thus was born the classical Darwinian view of the human tail, now a full-blown icon of evolution -- restated by physicist Karl Giberson in his recent debate with Stephen Meyer, which is why I bring the subject up now. This myth, which I'll be examining in future posts, holds that the "tail" is a regression to an earlier form, an expression of dormant genes retained from our ancient forebears.
A paper in the Journal of Neurosurgery explains that this view is itself a holdover from recapitulation thinking:
True human tails are rarely encountered in medicine. At the time when Darwin's theory of evolution was a matter of debate, hundreds of dubious cases were reported. The presence of a tail in a human being was considered by evolutionists as an example that "ontogeny recapitulates phylogeny."1Giberson seems to endorse a similar view of human tails, holding that they arise when vestigial genes are accidentally turned on. He is wrong on multiple levels. Firstly, as far as the medical literature reflects, not a single known human being has ever been born with, as he puts it, a "perfectly formed, even functional tail."
Human tails are extremely rare, with perhaps only a few hundred cases documented worldwide over the past half-century. Medical researchers who have had the lucky opportunity to study a human tail have divided them into two general categories: "true tails," which extend from the coccyx (tailbone) where one might expect a so-called "vestigial tail," and "pseudotails" which are often found in other locations on the lower back, and seem to be obvious aberrations since they are often associated with anomalies.
This distinction is based upon evolutionary assumptions, and in recent years it has become quite controversial as researchers have learned more about the phenomenon. I'll say more later about why even the "true tails" in humans don't deserve that name. For now, here's a crucial fact: even such so-called "tails" aren't anything like those found in tailed mammals. That is for the simple reason that "true tails" in humans entirely lack vertebrae -- or any kind of bone, cartilage, notochord, or spinal cord. As the aforementioned paper in the Journal of Neurosurgery explains:
In all reported cases, the vestigial human tail lacks bone, cartilage, notochord, and spinal cord. It is unique in this feature.2Other prominent medical research journals agree:
- A 2013 paper in the Journal of Child Neurology states: "True tails are boneless, midline protrusion usually attached to the skin of the sacrococcygeal region and capable of spontaneous or reflex motion. They consist of normal skin, connective tissue, muscle, vessels, and nerves and are covered by skin. Bone, cartilage, notochord, and spinal cord are lacking."3
- A paper from the Journal of Pediatric Surgery states: "The human vestigial tail lacks bone, cartilage, notochord, and spinal cord. It contains a central core of mature fatty tissue divided into small lobules by thin fibrous septa. Small blood vessels and nerve fibers are scattered throughout. Bundles of striated muscle fibers, sometimes degenerated, tend to aggregate in the center."4
- An article in the British Journal of Neurosurgery explains: "A true tail in humans is vestigial and never contains vertebrae in contrast to other vertebrate animals."5
- Most striking of all, perhaps, are the words of a famous paper on tails in The New England Journal of Medicine: "When the caudal appendage is critically examined, however, it is evident that there are major morphologic differences between the caudal appendage and the tails of other vertebrates. First of all, the caudal appendage does not contain even rudimentary vertebral structures. There are no well-documented cases of caudal appendages containi