What Is the Purpose of Appendix? Scientists Look for Answers in the Human Evolution

Projecting off the cecum in the digestive system is a small, thin, finger-shaped pouch known as an appendix. For many years, experts have believed that this hollow tube is a vestigial organ once used by our ancestors but has lost its function through evolution. Several hypotheses also link the purpose of the appendix to the diet of an organism and other environmental factors that affect its lifestyle.

Today, the appendix is considered no longer helpful, and removing it does not seem harmful to a person. However, the appendix is highly conserved in humans, suggesting an important role in that structure. For this reason, scientists have conducted studies trying to discover the purpose of the appendix in humans and other animals.

Finding the Purpose of the Appendix Using Genetic Tree

A recent study suggests that the appendix may serve an important purpose. In 2017, a group of international researchers from Midwestern University led by associate professor Heather F. Smith studied the evolution of appendix across mammals focusing on the presence or absence of appendix and other gastrointestinal and environmental traits.

Using data gathered from 533 mammal species, they made a phylogeny or genetic tree to track how the appendix might have evolved through mammalian evolution. They also used this data to determine why some species have appendixes while some do not.

The team discovered that in various mammal lineages, the appendix had evolved more than 30 separate times independently without disappearing from a lineage once it appeared. This discovery has led scientists to theorize the adaptive purpose of the appendix as a secondary immune organ. Since species with appendix were found to have higher concentrations of immune tissue in the cecum, it provides evidence that the appendix may serve as a "safe house" for beneficial gut bacteria.

In a separate study, scientists from France and Switzerland claimed that the immunological purpose of the appendix is an example of biological redundancy that ensures the robustness of organisms. By analyzing the caecal appendix, they studied its dual role as a primary site for immunoglobulin and a unique niche for commensal bacteria. The scientists conclude that the appendix might be redundant in its immunological purpose, but it is unique as a storage of microbiota.

Health Issues Involving the Appendix

In some cases, the appendix can become inflamed and infected, resulting in a health condition known as appendicitis. It is still unclear what causes appendicitis, but health experts suggest that it results from appendix luminal blockage. Some of the causes of this obstruction include intestinal parasites, abdominal injury or trauma, and enlarged lymph tissue of the appendix wall.

According to John Hopkins Medicine, 1 out of 1,000 people in the U.S. suffer from appendicitis, mostly individuals from 10 to 30 years of age. The risk can also be increased by a family history of appendicitis, especially in men, while a child has a higher tendency to acquire this disease due to cystic fibrosis.

As a medical emergency, appendicitis can cause serious, deadly infection if not treated immediately. The healthcare provider will advise the removal of this organ as soon as it is diagnosed. If not removed quickly, the appendix could burst, leading to infection in the belly, known as peritonitis.

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