August 24, 2020 | Jerry Bergman

The Thymus: Vestigial Not!

The Long Struggle Against Darwinists to Prove Its Important Functions

by Jerry R. Bergman

The thymus was firmly documented as a functional human body organ only in 1961 by Jacques Miller.[2] Miller’s discovery also laid the “foundation for immunology and modern medicine. Until that time, researchers mistakenly believed the thymus merely represented a remnant of defunct lymph tissue, something of an immune cell graveyard.”[3] Actually, over a half century earlier, in 1900, Dr. Richard Sheldon observed that the “useless organ” belief has hampered progress in understanding human biology and anatomy. He reviewed the research on the function of organs that were widely regarded in 1900 as useless. The list he made included, not just the appendix, but that very puzzling organ– the thymus. His belief in an intelligent creator made him confident that they both had functions and were not useless leftovers as taught by most evolutionists then.[4]

Over sixty years later, in 1961, Sheldon was vindicated by Jacques Miller’s discovery of immune responses being mediated by thymus-derived cells (now known as T-cells). In 2020 we now know that the thymus not only has a function, but a critical human-body function: the development of our immune system.  From this present-day vantage we can judge the long line of misleading evolutionary claims, such as by Nobel Laureate immunologist Sir Peter Medawar (1915-1987). His research on graft rejection and acquired immune tolerance are fundamental to tissue and organ transplants and as…

late as 1963, Sir Peter Medawar stated: “We shall come to regard the presence of lymphocytes in the thymus as an evolutionary accident of no very great significance. Lymphocytes are found in other evolutionary relics, such as the palatine and pharyngeal tonsils, which arise, like the thymus, from what used to be the pharyngeal epithelium, and it is the common lot of most of these relic organs to be infiltrated with lymphocytes.” [5]

Figure 1. The Location of the Thymus, from Lecture 20 Notes, Unit 204: Lymphatic tissue.

A Brief Discussion of Its Function

The thymus is a pinkish-gray bi-lobed gland located in the mediastinum area [central thorax] of the chest. It is below the larynx, under the sternum (breastbone), and superior to the heart. The thymus consists of two pyramidal-shaped lobes connected by an isthmus.[6]

The immune role of the thymus involves helping to establish the immune system by maturing the T-cells, the T refers to the thymus.  T cells (T lymphocytes) are often discussed in connection with the disease effects of AIDS.  As the T-cell count number goes down as a result of the virus attacking the T-cells, the immune system is correspondingly weakened. This T-cell drop results in diseases that the normal body with a healthy immune system can effectively control. As Professor Alberts, et al., explains,

Helper T cells are arguably the most important cells in adaptive immunity, as they are required for almost all adaptive immune responses. They not only help activate B cells to secrete antibodies and macrophages to destroy ingested microbes, but they also help activate cytotoxic T cells to kill infected target cells. As dramatically demonstrated in AIDS patients, without helper T cells we cannot defend ourselves even against many microbes that are normally harmless.[7]

The thymus cortex is composed of tightly-packed epithelial cells, lymphocytes, and macrophages.  Immature white blood cells migrate from red bone marrow to the thymus where they then proliferate and develop into mature T-cells. The thymus epithelial cells produce the thymic hormones that facilitate T-cell maturation. The thymus gland is comparatively large in infants, reaches its maximum size at about age 11, and then when its task in establishing the immune system has been achieved, it shrinks down to a maintenance role. At this time adipose and areolar connective tissue begin to replace thymus tissue.  This fact explains why thymectomy, “which had always been performed in adult animals, was not associated with any immune defects.” [8]

Figure 2. A diagram of the internal structure of the thymus showing the support cells.

The History of Understanding Its Function

Sheldon observed in 1900 that the “useless organ” belief has hampered progress in understanding both human biology and anatomy. He reviewed the research on the function of organs that were widely regarded in 1900 as useless. The list he made included, not just the appendix, but that very puzzling organ, the thymus.[9]

Then, in 1966, a popular article which observed that the thymus was long regarded a “useless gland” reviewed the research that documented its function.[10] After noting that, for generations, physicians viewed it “as a useless vestigial organ which has lost its original purpose if indeed it ever had one,” the article stated we now know that this organ serves to guard our health.[11]

The history that documented the resistance to the proven fact that it had an important function was summarized by Miller:

The lymphopoietic [poieses, meaning the formation, thus lymphopoietic means the formation of lymphocytes or lymphatic tissue] function of the thymus was firmly established only in the 1950s, yet immunologists were reluctant to accept its role in immunity. Thus, unlike circulating or splenic lymphocytes, thymic lymphocytes failed to adoptively transfer immunological capacity to immunodeficient animals. Antibody-forming plasma cells and germinal centers, so prominent in spleen and lymph nodes, never appeared in the thymus of normal immunized animals. Furthermore, thymectomy, which had always been performed in the adult, had never been associated with immune defects. All of these findings were cited as arguments against an immune function for the thymus, which was considered by many to be a vestigial structure, perhaps a “graveyard” for dying lymphocytes.[12]

The Thymus: Vestigial No More

How it was found out that the thymus has an important function is another example of the fact that empirical science research has caused a major problem for Darwinism from the very beginning, and is still so today:

In 1961, thymectomy was performed in mice during the immediate neonatal period and revealed the critically important function of the thymus in enabling the development of the immune system. Neonatally thymectomized (NTx) mice were highly susceptible to intercurrent infections, deficient in lymphocytes, unable to reject foreign skin grafts or produce antibody to some (though not all) antigens, and prone to developing certain tumors…. the thymus was responsible not only for the normal development of immune functions but also for imposing tolerance to the body’s own tissues.[13]

Thus, this research found the thymus had an important function throughout life. In short, the thymus was

shown to greatly influence T-cell development. They were able to educate T-cells to recognize a great diversity of peptide antigens bound to the body’s own markers ….. but purged any T-cells that strongly reacted against the body’s own self-components. …  T- cells were not the precursors of antibody-forming cells but were essential to help, through some type of collaboration, other lymphocytes originating in bone marrow (B cells) to respond to antigen by producing antibody.[14]

The critical importance of the discovery of the thymus functions brought about nothing less than a revolution in understanding how our body functions. As described by Miller,

the discovery of thymus function and of T and B cell collaboration was a major immunological milestone because it not only opened up the field of immune cell interactions but also changed the course of immunology and medicine. It promoted the need for all immune phenomena, for example, memory, tolerance, autoimmunity, and immunodeficiency, as well as inflammatory and immunopathological disease conditions, to be reassessed in terms of the role played by the two distinct sets of lymphocytes and their subsets. We now know that T-cells are involved in the entire spectrum of tissue physiology and … even in situations not considered to be bona fide immunological conditions, such as tissue repair, dysbiosis, eclampsia, senescence, and cancer.[15]

The thymus story is also another case of evolution blinders getting in the way of scientific research.[16] If we took seriously the observations of creationist Dr. Richard Sheldon, the importance of the thymus might have been understood much earlier, and progress in medicine would have moved forward much sooner.[17]


In chapter 17, Dr Bergman discusses the thymus gland.

[1] “Thymus: Vestigial No More” is the subheading in Miller, Jacques F.A.P. 2020. The function of the thymus and its impact on modern medicine. Science 369(6503):eaba2429, July 31.

[2] Miller, Jacques F.A.P. 1961. Immunological function of the thymus. The Lancet 278(7205):748–749, September 30.

[3] Editorial introduction to Miller, Jacques F.A.P. 2020. The function of the thymus and its impact on modern medicine. Science 369(6503): eaba2429, July 31. [p. 522] DOI: 10.1126/science.aba2429.

[4] The Story of Useless Organs by Richard M. Shelton. Reprinted from Getting Well, 1900, Mokelumne Hill, CA: Health Research, 248 pages. Reprint by Whitefish, MT: Kessinger Legacy Reprints, 2019, pp. 37-38.

[5] Miller, 2020, p. 524.

[6] Seeley, Rodney R.; Trent D. Stephens and Philip Tate. 2003. Anatomy and Physiology. Boston: McGraw-Hill Higher Education, p. 778.

[7] Alberts, Bruce, et al. 2002. Molecular Biology of the Cell, 4th edition. New York: Garland Publishing Co.,  p. 1193. Emphasis added.

[8] Miller, 2020, p. 523.

[9] The Story of Useless Organs by Richard M. Shelton. Reprinted from Getting Well, 1900, Mokelumne Hill, CA: Health Research, 248 pages. Reprint by Whitefish, MT: Kessinger Legacy Reprints, 2019, pp. 37-38.

[10] Maisel, Albert. 1966. “The Useless Glands that Guard Our Health.” Reader’s Digest. November, pp. 229-235.

[11] Maisel, 1966, p. 229.

[12] Miller, 2020, p. 524. Emphasis added.

[13] Miller, 2020, p. 523.

[14] Miller, 2020, p. 523.

[15] Miller, 2020, p. 523. Emphasis added.

[16] Bergman, Jerry. 2019. Useless Organs: The Rise and Fall of the Once Major Argument for Evolution. Tulsa, OK: Bartlett Publishing.

[17] Geenen, Vincent and Wilson Savino. 2019. History of the Thymus: From a Vestigial Organ to the Programming of Immunological Self-Tolerance. Thymus Transcriptome and Cell Biology. Springer, Cham. pp. 1-18.

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 1,300 publications in 12 languages and 40 books and monographs. His books and textbooks that include chapters that he authored are in over 1,500 college libraries in 27 countries. So far over 80,000 copies of the 40 books and monographs that he has authored or co-authored are in print. For more articles by Dr Bergman, see his Author Profile.

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