Science Literature

The evolutionary agenda for the human appendix was set by Charles Darwin in The Descent of Man (1871). In Chapter 1, he presented several evidences for our animal ancestry, some of which went under the name of 'Rudiments'. On pages 27-28, he has this to say:

"With respect to the alimentary canal I have met with an account of only a single rudiment, namely the vermiform appendage of the caecum. The caecum is a branch or diverticulum of the intestine, ending in a cul-de-sac, and it is extremely long in many of the lower vegetable-feeding mammals [. . .] It appears as if, in consequence of changed diet or habits, the caecum had become much shortened in various animals, the vermiform appendage being left as a rudiment of the shortened part. [. . .] Not only is it useless, but it is sometimes the cause of death, of which fact I have lately heard two instances: this is due to small hard bodies, such as seeds, entering the passage and causing inflammation."

This was the story that was passed to subsequent generations of biologists. It was endorsed by Ernst Mayr as recently as 2001: "Every shift into a new adaptive zone leaves a residue of no longer needed morphological features that then become an impediment. One only needs to think of the many weaknesses in humans that are remnants of our quadrupedal and more vegetarian past, for instance [. . .] the caecal appendix." (p. 143, What Evolution Is, Basic Books).
For many years, the only dissenting voices have been from creationists, who found some evidence of functionality. However, it would appear that those with specialist knowledge had quietly buried this 'evidence' for evolution, as is witnessed by this comment in a recent study of its functionality: "[The appendix was] often considered to be a vestige of evolutionary development despite evidence to the contrary based on comparative primate anatomy." The research is summarised thus in a news report:

The function of the appendix seems related to the large amount of bacteria populating the human digestive system, according to the study in the Journal of Theoretical Biology. There are more bacteria than human cells in the typical body. Most of it is good and helps digest food.
But sometimes the bacteria in the intestines die or are purged. Diseases such as cholera or amoebic dysentery would clear the gut of useful bacteria. The appendix's job is to reboot the digestive system in that case.
The appendix "acts as a good safe house for bacteria," said Duke surgery professor Bill Parker, a study co-author. Its location -- just below the normal one-way flow of food and germs in the large intestine in a sort of gut cul-de-sac -- helps support the theory, he said.

It might be hoped that Darwinian evolutionary biologists would acknowledge that errors have been made; that Darwin's claim for the appendix being useless was a claim made from ignorance rather than knowledge; that their theory had coloured their understanding of the data; etc. But no - what we get is this response to the new research:

The idea "seems by far the most likely" explanation for the function of the appendix, said Brandeis University biochemistry professor Douglas Theobald. "It makes evolutionary sense."

It makes evolutionary sense ONLY because evolutionary theory is apparently infinitely adaptable to data and the storytelling mentality prevails.
It should be remembered that functionality was the prediction of biologists with a creation or design mentality, and it was not the prediction of evolutionary biologists. On this occasion, the people with a design perspective were right and the Darwinians were wrong. Let's remember this next time we hear creation or ID being decried as being unable to make any scientific predictions!

Biofilms in the large bowel suggest an apparent function of the human vermiform appendix
R. Randal Bollinger, Andrew S. Barbas, Errol L. Bush, Shu S. Lin and William Parker
Journal of Theoretical Biology, 249(4), 21 December 2007, 826-831.

Abstract: The human vermiform ("worm-like") appendix is a 5 to 10 cm long and 0.5 to 1 cm wide pouch that extends from the cecum of the large bowel. The architecture of the human appendix is unique among mammals, and few mammals other than humans have an appendix at all. The function of the human appendix has long been a matter of debate, with the structure often considered to be a vestige of evolutionary development despite evidence to the contrary based on comparative primate anatomy. The appendix is thought to have some immune function based on its association with substantial lymphatic tissue, although the specific nature of that putative function is unknown. Based (a) on a recently acquired understanding of immune-mediated biofilm formation by commensal bacteria in the mammalian gut, (b) on biofilm distribution in the large bowel, (c) the association of lymphoid tissue with the appendix, (d) the potential for biofilms to protect and support colonization by commensal bacteria, and (e) on the architecture of the human bowel, we propose that the human appendix is well suited as a "safe house" for commensal bacteria, providing support for bacterial growth and potentially facilitating re-inoculation of the colon in the event that the contents of the intestinal tract are purged following exposure to a pathogen.

See also:

Borenstein, S., Appendix is a refuge for good germs, study says, The Associated Press, Oct 06, 2007.