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From the Steadily Shrinking Catalogue of "Functionless," "Vestigial" Organs: Now, the Tailbone

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Recently I was invited to give a talk on the evidence for intelligent design to a course at a state university. One of the questions that came up in the Q&A was whether there is a function for the coccyx, commonly called the tailbone. I explained that the tailbone is not a useless vestigial organ, but has function: it serves as an attachment point for various muscles and tendons. Afterwards, the professor noted that some individuals have had their tailbones surgically removed, implying that it may be superfluous.

Most Darwinian evolutionists view the tailbone as a vestigial organ, derived from our purportedly tailed ancestors, whose purpose now is either reduced or non-existent. Evolutionists who claim the tailbone has a function, but a “reduced” one, offer a conveniently untestable argument. They say that even though it may do something today, at some point in the past it did more. How could you ever disprove such an assertion?

More often we hear evolutionists claiming that the tailbone has no function whatsoever, and in fact that is what the professor seemed to be suggesting. A student in the class emailed me to ask about what the professor said. Here’s what I said in response.

It doesn’t surprise me if people can have their tailbones removed and still survive. Just because you can live without a tailbone doesn’t mean it doesn’t have a function. People can also live with one kidney instead of two. We can lose the hair on our head, but it has a function. Many people throughout human history have lived after losing many if not most of their teeth — but teeth certainly have a function.

If you break your tailbone, it can be extremely painful. I assume that anyone who had his tailbone removed did so only because of some severe medical problem that caused great pain (like a broken or dislocated tailbone). Only then is it better to have it removed. Most likely this required fairly complex surgery both to remove the tailbone and then to reattach the muscles that normally attach to it to other lower vertebrae.

None of this suggests that the tailbone isn’t an important anatomical feature that does important things.

In fact a number of online medical sources discuss various functions of the tailbone:

  • “The coccyx serves as an attachment site for tendons, ligaments, and muscles. It also functions as an insertion point of some of the muscles of the pelvic floor. The coccyx also functions to support and stabilize a person while he or she is in a sitting position.” (Healthline.com)
  • “Function of coccyx: It is believed that the coccyx is remnant of vestigial tail. But it is not useless in the body. It provides attachment to various important muscles, ligaments, and tendons. Additionally, it is also a component of the weight bearing structure during sitting position.” (manatomy.com)
  • “The tailbone derived its name because some people believe it is a ‘leftover’ part from human evolution, though the notion that the tailbone serves no purpose is wrong. The coccyx is an extremely important source of attachment for tendons, ligaments, and muscles, though it is structured quite differently than other parts of the spine. … Muscles that attach to the tailbone and contribute to sitting, standing, and bowel control include:
    Gluteus maximus — large gluteal muscle; helps keep body erect
    Levator ani — thin muscle; helps support organs of the pelvis
    Sphincter ani externus — flat muscle; assists in bowel function
    Coccygeus — triangular muscle; supports the pelvic floor” (Laser Spine Institute)
  • The coccyx’s “anterior flexion when sitting however, indicates that it may bear some weight during sitting. It is nevertheless an important part of the spinal column as it serves as a site of attachment for various muscles and ligaments.” (Healthhype.com)
  • “Some fibers of the gluteus maximus attach directly to the sides and back of the coccyx and resist the pull (flexion) of the coccygeal pelvic floor muscles mentioned above” (malepelvicfloor.com)
  • “Many of the muscles of the lower pelvis attach to the coccyx. These muscles form a ‘pelvic floor.’ When these muscles do not function properly, bowel, bladder, and sexual problems are more likely to occur. Malposition of the coccyx (coccygeal subluxation) may be a factor in the dysfunction of these pelvic floor muscles.” (Chiroweb.com)

Each of these medical websites notes that the coccyx is an attachment site for muscles, and many also note that it is an important attachment site for tendons and ligaments. Some of the websites note that the coccyx has a weight-bearing function when we sit. Definitely not functionless!

Evolutionary thinking can hinder the progress of science by wrongly presuming that functional parts are vestigial holdovers, and have no function. Evolutionists, it seems, may not fully appreciate the meaning of “function” as we understand it within a paradigm of intelligent design.

ID views parts of a system as comprising an integrated whole. Perhaps the system can still work without certain parts, but its efficiency will be diminished. For example, you can drive a car without a hood or side mirrors, but that doesn’t mean those parts don’t perform important functions.

The theory of intelligent design does not demand that the coccyx be medically indispensable. Rather, ID expects that the coccyx will have some function that contributes to the integrated whole. In that regard, the coccyx clearly has multiple functions — and thus fulfills the predictions of intelligent design.

Image by Steve Jurvetson from Menlo Park, USA (dem bones) [CC BY 2.0], via Wikimedia Commons.