The  appendix, a narrow pouch in the digestive system that has a notorious reputation for its tendency to become inflamed (appendicitis, may have important function, new research suggests. .Dr Heather F. Smith,  Associate Professor, Midwestern University Arizona College of Osteopathic Medicine, is currently studying the evolution of the appendix across mammals.

Smith’s international research team gathered data on the presence or absence of the appendix and other gastrointestinal and environmental traits for 533 mammal species. They mapped the data onto a phylogeny (genetic tree) and to try to determine why some species have an appendix while others don’t.

They found that species with an appendix have higher average concentrations of lymphoid (immune) tissue in the cecum. This finding suggests that the appendix may play an important role as a secondary immune organ. Lymphatic tissue can also stimulate growth of some types of beneficial gut bacteria, providing further evidence that the appendix may serve as a “safe house” for helpful gut bacteria.