American researchers have found that the appendix has a function, has been in existence for 80 million years and are present in other species other than humans.

The sac hanging between the small and large intestine serves as a "safehouse" of good bacteria that spreads on the intestine after others have been wiped out during a diarrhea attack, according to the researchers from the Duke University Medical Center in Durham, North Carolina led by immunologist William Parker.

Parker and his colleagues also found that the appendix can help produce white blood cells and train these on how to fight intections.

Many species of monkeys and rodents also possess what evolutionist Charles Darwin termed as the remnant of a cecum, a food digester in extinct animals, the researchers said. They added that it was around among wombats, lemmings and meadow voles of Australia as early as 80 million years ago.

The findings of Parker and his colleagues were published in the August 12 issue of the Journal of Evolutionary Biology.