A mysterious organ of the human body lies behind the sternum (breastbone) and in front of the heart. It’s called the thymus. Almost 2000 years ago, the Greek physician and surgeon Galen of Pergamon called it the “seat of the soul.” However, as recently as 1961, Nobel Prize-winning British biologist Sir Peter Medawar called the thymus the graveyard for dying cells and “an evolutionary accident of no very great significance.” Today, scientists know that the thymus has an essential purpose in establishing the immune system during childhood and continues to be beneficial throughout life. Since the thymus has been known for thousands of years, why did it take so long for science to discover that it has a purpose?
Recent research at Massachusetts General Hospital has shown the role the thymus plays in a person’s health. It helps regulate aging and immune health. It appears to play a crucial role in a person’s longevity, protecting against cancer, autoimmune disease, and even cardiovascular risks. Medical scientists have found that people with healthier thymuses are less likely to develop lung cancer or die of heart disease or other causes.
The thymus has sometimes been removed because it can get in the way of heart or chest surgery, and the removal is called a thymectomy. In the past, thymectomy was not considered a problem because people seemed to get along very well without the thymus. The research team found that people receiving a thymectomy were more likely to die of any cause within five years than people with a healthy thymus. People without a thymus were twice as likely to develop cancer and were also more likely to develop autoimmune disease.
The thymus has an essential purpose and is not a vestigial organ, as some have thought in the past. It is not a mistake of evolution. A healthy thymus is a predictor of good health in many respects. People with healthy thymuses are less likely to develop lung cancer or die of heart disease. They are also more likely to respond positively to cancer drugs. The research has led to interest in finding ways to slow the thymus’s natural deterioration, which occurs in adulthood.
Too often, we have been led to believe that something is a vestigial organ, leftover from the process of evolution, when, in fact, it plays a role in our health. (For example, tonsils, appendix, and so-called “junk DNA.”) Looking at medical research from an evolutionary viewpoint can sometimes lead to neglect of important health issues. If we believe our bodies are intelligently designed rather than merely accidents of evolution, we have a reason to look for that design. The thymus has an essential purpose because God designed it that way, but science overlooked it for way too long.
— Roland Earnst © 2026
References: washingtonpost.com, and New England Journal of Medicine HERE and HERE