Do humans have a tail? This article looks at the development of the human embryo and evolutionary theory.

Source: The Outlook, 1986. 2 pages.

Human Tails

Did you ever hear of people having a tail? It may seem strange, but we do. But only when we are very small, long before we are born. So let's look at what the situation is at our beginning stages.

After the human ovum is fertilized it takes about four days to travel through the uterine tube and to ar­rive in the uterus. Then, on about the ninth day after fertilization, it is implanted into the lining of the uterus. At this time a vigorous growth period begins. From implantation up to the tenth week this new in­dividual, who is developing in the womb, is called an embryo. After that it is called the fetus.

When the embryo is four weeks old and about 4 mm. long, the backbone is taking shape, including some tailbone features. At this stage the end of the backbone projects from the body, very similar to that of a pig of 4 mm. and to other animals at a comparable stage. Some people think that this should make us Christians uncomfortable, because they think that this would indicate that we developed from animals through evolution. But we need not at all be uncom­fortable about this. And it does not indicate that we evolved.

In a classic example in an older textbook of Em­bryology, the authors, discussing the development of the lower end of the spine, say

It is interesting that at this state (ca. 5 weeks – AM) the human embryo has every bit as well developed a tail as a pig. The tail in our own later development normally undergoes regressive changes that leave us with only our symbolic coc­cyx. Occasionally, to the discomfiture of anti-evolutionists, this regression fails to occur, and a human infant is born with a sizable and unmis­takable tail.1

The authors thus indicate that they see a problem for us.

A closer look shows us, first of all, that they are cor­rect in saying that we have a tail at that stage, and that it is as well developed as that of a pig of that stage (not of an adult pig, of course). That there is a tail is a well-established fact. To be more specific, that tail consists of the end of the vertebral column. And it is so noticeable because there are no legs yet to obscure its presence. At this time the legs are only just begin­ning to form as little paddle-shaped buds. It doesn't take long, however, before these leg buds elongate, develop bones and muscles, and start looking like regular tiny baby legs. And in so doing they grow around that early tail-like structure, which is really the end of the spine, so that definitive relationships can be established. In adults there is still that tail bone, but the end of the spine is then surrounded with hip and leg structures, such as bones, muscles, nerves, and blood vessels, all of which are necessary for normal functioning.

Secondly, what about being left "with only our symbolic coccyx?" The question is, then, "Of what is it symbolic?" The intention is obviously to suggest that it symbolizes our animal ancestry. But it sym­bolizes that only to those who have faith in the story of evolution. In actual fact, the coccyx is just an adult structure which is necessary, and without which we would have difficulty functioning normally. And the muscles which attach to that part of the spine have definite and useful functions. After all, there has to be some kind of end to the vertebral column.

Finally, what about the occasional infant that is "born with a sizable and unmistakable tail?" This is not any different from occasional children being born with other abnormalities, and indicates only that in the development of this individual something went wrong at a particular time in that specific location. And the tail that is sometimes depicted in textbooks is not the end of the vertebral column, as it would have to be in order to be homologous with the pig's tail, but only a fleshy one, which can be removed surgically, without involving the vertebral column.

In pigs the story goes a little different, because there the legs grow along the spine, too, but their corkscrew tail does stick out beyond the end of the body, as it was designed to do.

There are many other similarities in the develop­ment of people and pigs as well, both in structure and in developmental control mechanisms. Not only are the eyes and ears similar in their development, but so are the early stages of the brain, the digestive system, the skin, and the kidneys, to name only a few. And the control mechanisms and principles that govern the regular development of the bones and mus­cles of legs and arms also are very similar in both.

In graduate school a lecturer once made a point of telling us about the many similarities between human and pig skin. These striking similarities were, of course, real. By pointing this out he wanted to sug­gest our evolutionary relationship to pigs. But it is natural that the structural and developmental plan for various creatures with backbones is similar, and to us this is exactly what we would expect when we believe that an all-wise Creator designed the plan for both.

The point is that in both man and pig these early relationships are necessary for the adult structures to be in the proper place at the right time. It is because of the common plan of development which the Creator designed for both of these organisms that they have similar developmental stages.

The idea of a human tail is indeed a little strange, or at least unexpected. But it is strange only until we think through the facts of embryonic development. Then we see the marvel of that common plan with its many variations, each one culminating in a perfect organism, and each organism fitting into its environ­ment just the way the Lord wanted it, and all of them together fitting into a fine-tuned complex system.

Should we be uncomfortable about knowing that human embryos have a tail-like structure in very early development? Not at all. Knowing that the design calls for that stage so that adult structures can func­tion properly is just something that we marvel at. And should you hear, or read, any talk about facts like these being evidence for a supposed slurring-over of our ancestral animal stages, you can just discount it. Such talk has no scientific value. It only serves to soothe the minds of unbelieving scientists who fail to acknowledge the great Designer who called forth these creatures by the power of His Word. And there is no need for Christians to jump on the evolutionist's bandwagon so that they might gain respectability. Compromise may result in acceptance into the secular community, but only at great cost. It creates tension with both the reality of created structure and the scrip­tural perspective on that created structure.

This knowledge, of how the spine and legs develop, fitted into the framework of a biblical view of reality, gives us a scientifically respectable picture and a glimpse of the truth here revealed. We can only mar­vel at the fact that we can actually understand this little part of the full story of human development in the womb.

Endnotes🔗

  1. ^ B. M. Patten and B. M. Carlson. Foundations of Embryology, 3rd Ed. McGraw-Hill Book Comp., New York, 1974, p. 291. Dr. Aaldert Mennega is Professor of Biology at Dordt College, Sioux Center, Iowa.

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