Tale of the Tail: Why the Human Coccyx Is Not a Vestigial Organ

Tall tales about the loss
of the human tail
continue to mislead

 

The Critical Importance of the Once Touted Vestigial Organ, the Coccyx

by Jerry Bergman, PhD

For over a century, the human coccyx was considered a useless remnant left over from our evolutionary past. Thus it was deemed a useless vestigial organ. Ironically, although its many important functions are well documented, the coccyx is still considered a useless remnant by certain evolutionists. Ewin Callaway writes in the scientific journal Nature that “Unlike most monkeys, apes — including humans — and their close extinct relatives don’t have tails. Their coccyx, or tailbone, is a vestige of the vertebrae that constitute a tail in other animals.”[1] For his conclusions, Callaway relied on the research of Harvard geneticist Bo Xia.[2] Xia explained their research “begins to explain how evolution removed our tails, a question that has intrigued me since I was young.”[3]

In short, when comparing the DNA of tailless apes and humans to that of tailed monkeys, Xia and his team found a DNA insertion shared by tailless apes and humans, but missing in tailed monkeys. They found no evidence for evolution, only a genetic difference between tailed and tailless primates.

Background of the Tail Loss

Orthodox evolutionary theory assumes that the human tail loss

happened around 25 million years ago (for comparison our common ancestor with chimps was [he claimed] about 6 million years ago). We still have the coccyx as an evolutionary hangover from this tail-bearing ancestry.”[4]

If humans lost their tail about 25 million years ago, then we have possessed a useless coccyx for about 25 million years. A 2023 article in one popular website stated that the coccyx was one structure which

remained in the human body despite having little to no function for millions of years…. Tailbones helped our ancestors with mobility and balance, but the tail began disappearing around 20 million years ago. The coccyx now serves no purpose in humans.… Our ancestors who had mutations that got rid of the tail seemed to fare better, and thus our tails went away over many generations.[5]

So much for evolutionary fiction.  The medical community has known for decades that the coccyx is anything but useless. A National Institutes of Health (NIH) website accurately reported that

Despite its small size, the coccyx has several important functions. Along with being the insertion site for multiple muscles, ligaments, and tendons, it also serves as one leg of the tripod—along with the ischial tuberosities—that provides weight-bearing support to a person in the seated position.[6]

Its importance was described by one anatomist who specializes in this structure, explaining in some detail that the coccyx is an integral part of the body. He writes:

The coccyx is a triangular bone that consists of 3 to 5 fused segments, the largest of which articulates with the lowest sacral segment. In addition, the first coccygeal segment contains …  processes called the coccygeal cornua that articulate with the sacral cornua. The lower part of the filum terminale, also called the coccygeal ligament, inserts onto this first segment. The coccyx is bordered anteriorly by the levator ani muscle and the sacrococcygeal ligament. Moving anteriorly to posteriorly, the lateral edges serve as insertion sites for the coccygeal muscles, the sacrospinous ligament, the sacrotuberous ligament, and fibers of the gluteus maximus muscle. Inferiorly, the iliococcygeus muscle tendon inserts onto the tip of the coccyx. These ligaments and muscles help support the pelvic floor and also contribute voluntary bowel control.[7]

The importance and accuracy of this article was indicated by the fact that it satisfied certification for “the Accreditation Council for Graduate Medical Education and the American Board of Medical Specialties Maintenance of Certification Competencies for Patient Care and Medical Knowledge.” This certification is required to maintain a medical license.

Unfortunately, in spite of this endorsement by the medical community, misinformation about the topic of vestigial organs is still common, partly because it is still a main support for the evolutionary narrative. Besides the National Institutes of Health, creationists have been actively attempting to correct the erroneous information on the coccyx for several generations. For example, I published a book on this topic 34 years ago titled, “Vestigial Organs” are Fully Functional: A History and Evaluation of the Vestigial Organ Origins Concept (with George Franklin Howe, Ph.D.; Forward by David Menton, Ph.D., Washington University School of Medicine; Preface by V. Wright M.D., F.R.C.P., Professor, University of Leeds).  The book was widely distributed; WorldCat lists 117 university libraries with a copy.[8]

How Evolutionary Assumptions Distort Reality

Based on the assumption that humans evolved from some ape ancestor, evolutionists attempt to explain not only why but “how humans lost their tails.”[9] One theory is, evolutionists conclude, that research has “identified a genetic change shared by humans and other apes that might have contributed to their ancestors’ tail loss, some 25 million years ago.”[10] The genetic reason for the loss was that “primates with tails lack a certain DNA insertion in a gene called TBXT.”

Genetic research has also determined that mice “carrying similar alterations to their genomes had short or absent tails.”[11] In other words, the newest claim is that a new or modified gene evolved that caused the loss, or shortening of, the tail in humans and mice. It caused this change by an insertion that leads to a shortened form of the protein that TBXT encodes. The shortening occurs after the gene is transcribed into messenger RNA, and when multiple protein-encoding segments of the gene transcript are spliced together.

What the Genetic Analysis Found

The only thing that the Bo Xia research team has determined was that a difference of the TBXT gene system exists in some animals that either lacked a tail or had a short tail. The result is that animals that lack this modification have long tails. Darwinists’ evolutionary perception forces them to conclude that a gene change in the TBXT produced short or no tails. Evolutionists have no evidence of this change occurring in evolution, only evidence of a difference between modern animals with no tails and those with tails.

Given the evolutionary perception, natural selection would have evolved a tail, or a longer tail, by modifying the TBXT gene system. This change, though, the researchers conclude, is actually very complex, a fact that argues against evolution as the source of the difference. A similar TBXT gene exists just a short distance away. The effect of these two genes existing in close proximity alters the processing of the resulting TBXT messenger RNA which makes the protein. The two RNAs then stick to each other, causing the RNA block between them to be excluded from the RNA that codes for the protein, resulting in a shorter protein.

Complications in the Research Results

The only animals discussed were primates and mice, consequently how far beyond these two animals this tail change can be generalized is unknown. A further problem was that the Xia researchers only analyzed 140 genes involved in tail development but identified thousands of other genetic changes that were unique to apes that could also have played a role in tail loss.[12] Thus, they must assume that de-evolution of the tail could have involved thousands of genes. Also, the fact that mandrills, some macaques, and lorises all lack tails, has resulted in the researchers “suggesting that the trait evolved multiple times.”[13]

Evolutionary Speculation

Articles referring to the Xia team’s research implied, or stated, that scientists have now concluded that losing the tail provided “our ape ancestors with an evolutionary advantage.”[14] One report stated, “We have then a strong candidate for a mutational change that underpins the evolution of being tailless.”[15]

Why tails evolved is similarly explained only by mere speculation: Reptiles, insects, birds, and mammals have evolved tails to serve a wide variety of purposes, including everything from achieving body balance, to a means of communication, to an aid in finding or attracting mates or even as a means of defense. Many primates have prehensile, or grasping, tails that function like hands to allow them to hold onto tree limbs. Given these many important uses, evolutionists have been pressed to explain the evolutionary advantage of losing their tails. One explanation for why humans lost their tail employed the Larmarkian use/disuse theory:

The loss of a tail in humans is thought to be related to the evolution of bipedalism. As our early ancestors began to walk upright, the need for a tail for balance and movement decreased. Instead, our hands became more important for manipulating objects and tools. Over time, the tail became less prominent and eventually disappeared. This adaptation allowed for greater dexterity and mobility, which may have provided an evolutionary advantage in various aspects of survival and adaptation to different environments.[16]

This attempts to explain tail loss in humans, but explaining its loss in other primates remains a challenge.

Summary

The Xia team identified that primates without a tail had at least one additional DNA sequence that they assume can transfer the tail-determining gene, TBXT, to new areas of a genome. Thus this explanation repeats the long-disproved claim that “the coccyx is an evolutionary hangover of the evolution of being tailless.”[17] The article closes with the observation that the Xia research documents

how misleading the march of progress [commonly used to picture evolution, see illustration] really can be. Evolution can only deal with the variation that is present at any time. And, as this latest study shows, many changes also come with costs. Not so much a march [forward] as a drunken stumbling.[18]

Although, from evolutionary theory, exactly why apes lost their tails is unknown, this problem has not stopped speculation:

the reason why apes lost their tails in the first place is uncertain, some scientists [believe that] not having a tail may have been better suited for vertical bodies living on the ground. Tailed primates generally use these appendages to help them swing from tree branches and walk on along them horizontally. Gibbons and orangutans are tailless apes that still live in trees, but they move differently than monkeys who have tails and hang below branches.[19]

This explanation explains the reason for the tailless design but does not address how it could have evolved in the first place.

References

[1] Callaway, Ewin. “How humans lost their tails — and why the discovery took 2.5 years to publish.” Nature; https://www.nature.com/articles/d41586-024-00610-x, 28 February 2024.

[2] Xia, B., et al. “On the genetic basis of tail-loss evolution in humans and apes.” Naturel doi.org/10.1038/s41586-024-07095-8, 2024.

[3] NYU Langone. “Research identifies genetic change associated with human tail loss;” Medical News Net, 2024.

[4] Hurst, Laurence D. “Losing their tails provided our ape ancestors with an evolutionary advantage – but we’re still paying the price.” The Conversation; https://theconversation.com/losing-their-tails-provided-our-ape-ancestors-with-an-evolutionary-advantage-but-were-still-paying-the-price-224385, 28 February 2024.

[5] Kotecki, Peter, et al. “9 useless body parts that humans no longer need.” Business Insider; 11 August 2023.

[6] Lirette, Lesley, et al. “Coccydynia: An overview of the anatomy, etiology, and treatment of coccyx pain.” Ochsner Journal 14(1): 84–87, Spring 2014.

[7] Lirette, et al., 2014

[8] Bergman, Jerry, and George Franklin Howe. “Vestigial Organs” Are Fully Functional: A History and Evaluation of the Vestigial Organ Origins Concept. Creation Research Society Books, Terre Haute, IN, 97 pp., 1990.

[9] Callaway, 2024.

[10] Callaway, 2024,

[11] Callaway, 2024.

[12] Xia, B., et al., 2024.

[13] Callaway, 2024.

[14] Hurst, 2024.

[15] Hurst, 2024.

[16] Super, Daniel. “Why was it an evolutionary advantage for humans to lose the tails that monkeys have?” Quora.

[17] Hurst, 2024.

[18] Hurst, 2024.

[19] Baisas, Laura. “Why we don’t have tails.” Popular Science; 2024.

[20] Bergman, Jerry. “The Ape-to-human Progression: The Most Common Icon is a Fraud.” Journal of Creation. 23(3):16-20. 2009.

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Dr. Jerry Bergman has taught biology, genetics, chemistry, biochemistry, anthropology, geology, and microbiology for over 40 years at several colleges and universities including Bowling Green State University, Medical College of Ohio where he was a research associate in experimental pathology, and The University of Toledo. He is a graduate of the Medical College of Ohio, Wayne State University in Detroit, the University of Toledo, and Bowling Green State University. He has over 1,900 publications in 14 languages and 40 books and monographs. His books and textbooks that include chapters that he authored are in over 1,800 college libraries in 27 countries. So far over 80,000 copies of the 60 books and monographs that he has authored or co-authored are in print. For more articles by Dr Bergman, see his Author Profile.