Home > Human Tails, Spleens And Other Not-Vestigial Organs

Human Tails, Spleens and Other Not-Vestigial Organs

from the May 13, 2014 eNews issue
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A five-month old baby boy in China born with a “tail” was recently diagnosed with tethered cord syndrome. While it looks on the surface as though he has regressed to his evolutionary past, instead the child has a disorder in which tissue attachments cause abnormal stretching of the spinal cord. The tail contains no bones or other tail structures; the poor child simply suffered improper growth of the neural tube during his fetal development.

The birth defect is closely related to spina bifida and can cause pain and problems with bowel and bladder control. Surgery early on can repair the congenital deformities, but follow-up care is needed to ensure that retethering doesn’t occur.

Darwin noted that humans were occasionally born with tails, and he saw these as vestigial body parts popping back up from humanity’s less-evolved genetic history. In reality, human tails are the result of developmental problems in the womb, and the organs that have long been considered “vestigial” actually serve important purposes.

Human Tails

Ernst Haeckel’s idea that embryos go through developmental stages that represent their evolutionary ancestors has long been discredited. Humans never go through a chick or fish stage, and their developing pharyngeal arches never work like gills. Yet, the evolutionary argument remains that humans have the unused genes to grow tails, that they develop tails in the womb, and sometimes they are born with these tails as evolutionary throw backs. The human “vestigial tail” is often used as an argument for macroevolution.

Humans do have “tails” that extend past their spinal column early in development, but these tails are naturally reabsorbed as the body grows. The spinal column itself is longer than the rest of the growing baby early on, and even calling the small poking extension beyond the spine a “tail” raises confusion. These protrusions are not actually tails in the sense that animals have tails. They don’t contain vertebrae or even bones. They are just extra tissue projecting at the end of the spinal column, and if they are not properly absorbed during development, the baby can be born with a fatty tail.

Casey Luskin recently tackled the issue of human tails in the article, “Are Humans Ever Born with “Perfectly Formed” Tails?” He refers to an October 1991 article in the Journal of Pediatric Surgery, which 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.”

In other words, it’s not a tail. It’s extra tissue that is out of place and protruding from the spine — often in an uncomfortable and potentially dangerous way.


Scientists have long considered the appendix an unnecessary vestigial organ with no purpose, because it could be removed with no apparent harm to the body. During the past few decades, researchers have suggested that the appendix does serve a useful function of holding good bacteria in reserve for the body in case disease ravages all of the bacteria in the gut. It acts as a protective cave where advantageous bacteria can hide until the disease is past and they can reboot the gut with necessary flora for digestion. The appendix also contains endocrine cells and appears to serve highly important hormonal and immune system functions during embryonic development and early childhood.

Oklahoma State University physiology professor Loren G. Martin wrote in Scientific American, “During the early years of development, however, the appendix has been shown to function as a lymphoid organ, assisting with the maturation of B lymphocytes (one variety of white blood cell) and in the production of the class of antibodies known as immunoglobulin A (IgA) antibodies. Researchers have also shown that the appendix is involved in the production of molecules that help to direct the movement of lymphocytes to various other locations in the body.”

Once we grow up it’s not as vital, and removing an inflamed appendix before it erupted has saved many lives. Still, just because one can live without a thumb doesn’t mean that thumbs are not useful — and so with the appendix. We still need gut flora to digest our food properly and to fight off harmful bacteria, and having an extra store on hand is useful.


The spleen is another organ long considered disposable. It does filter the blood, removing old and damaged red blood cells, but we can live without it. A 2009 study showed, however, that the spleen serves a purpose more important than previously understood. The spleen stores an essential white blood cell called a monocyte. Monocytes not only race to injured tissue and turn into macrophages, which eat debris and pathogens, but they can also serve to repair damaged tissue. It has long been known that monocytes are made in the bone marrow, but they are also stored in large amounts in the spleen, making it an important arsenal for immune response. Monocytes are instrumental in repairing damaged heart tissue after a heart attack, so the 40—50% of monocytes that come from the spleen are significant to heart patients.

The body has been created with a lot of room for changing plans. There is duplication of function in many parts of the body, so that if one organ stops working so well, another can make up for it. We can take a licking and keep on ticking. Yet, each part serves a necessary role, and the body works best if all the various parts are healthy and working together. Just because we can live without certain organs doesn’t mean it’s best that way.

The human tail demonstrates that errors cause deformity, not new, exciting body parts with additional function. It is not a shadow of the tails we had in past evolutionary lives. The appendix is rare in the animal kingdom and was long considered useless. Yet it has supposedly evolved independently more than 30 times in creatures not closely related to each other. If similar organs indicate descent from a common ancestor, then why have so many diverse creatures evolved the appendix?

We’re grateful for those scientists out there working to get to the heart of the matter, who ask questions like, “Why the appendix?” and hunt until they find answers for us. We’re grateful for the brilliant Mind behind every cell in our bodies, who gave us immune systems and circulatory systems and skeletons to hold us up in the first place, who gave us brains to understand the brilliance of His handiwork and hearts to know Him.



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