Saturday science subject: The friendly appendix


— 2:50 PM on August 22, 2009

Widely thought to be a useless vestigial structure, the human appendix may actually have evolved for a reason—to act as a safe house for "good" bacteria needed to maintain our gut flora. According to ScienceDaily, the Duke University researchers who put forward that hypothesis have carried out a new study of "the appendix through the ages" together with collaborators from the University of Arizona and Arizona State.

Using a modern approach to evolutionary biology called cladistics, which utilizes genetic information in combination with a variety of other data to evaluate biological relationships that emerge over the ages, [Duke University Assistant Professor William Parker] and colleagues found that the appendix has evolved at least twice, once among Australian marsupials and another time among rats, lemmings and other rodents, selected primates and humans. "We also figure that the appendix has been around for at least 80 million years, much longer than we would estimate if Darwin's ideas about the appendix were correct."

Additionally, the study demonstrates that the appendix coexists with a "large cecum which is used in digestion" in some existing species. That evidence goes against the notion that the human appendix is the modern remnant of a now-bygone cecum. Appendices are also surprisingly common. "For example, when species are divided into groups called 'families', we find that more than 70 percent of all primate and rodent groups contain species with an appendix," says Parker.

So, if the appendix is supposed to be there, why can it randomly get infected and kill us? Parker believes changes brought about by modern sanitation may be to blame. "Those changes left our immune systems with too little work and too much time their hands – a recipe for trouble," he says. Preventing appendicitis, along with a host of other allergic and autoimmune conditions, could be as simple as using modern medicine to challenge our immune systems "in much the same manner that they were challenged back in the Stone Age."

 
   
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