The human appendix is often held up as an example of a vestigial organ - something that is much reduced in form from the homologous structure in other organisms (though not necessarily also non-functional). Darwin wrote a little bit about our appendix in The descent of man. Now it seems that a research team has done a bit of molecular detective work & claims that appendices aren't vestigial at all. PZ Myers has the first part of a very thorough coverage of this over on Pharyngula, dealing with the suggestions that 'Darwin was wrong' (which are just begging to be quote-mined by the creationist lobby). (He says he'll post 'part II' soon - it would have been a mammoth post if he'd done the lot at once! PS & here it is.)
PZ starts off by quoting a press release from the research team's home institution:
Now, some of those same researchers are back, reporting on the first-ever study of the appendix through the ages. Writing in the Journal of Evolutionary Biology, Duke scientists and collaborators from the University of Arizona and Arizona State University conclude that Charles Darwin was wrong: The appendix is a whole lot more than an evolutionary remnant. Not only does it appear in nature much more frequently than previously acknowledged, but it has been around much longer than anyone had suspected.
"Maybe it's time to correct the textbooks," says William Parker, Ph.D., assistant professor of surgical sciences at Duke and the senior author of the study. "Many biology texts today still refer to the appendix as a 'vestigial organ.'"
Now, can you see the glaring straw man argument right there? Darwin mentioned the human vermiform appendix only, not the appendix as part of a generalised gut, & that rather briefly, saying that it was significantly reduced in size from the same organ in many other mammals.
Yet another paper for me to try to find time to read :-)