an appendix to evolution…
How many times have you heard that something is as useless as an appendix? Well, a new paper aims to revise that saying. Rather than being completely useless, it looks like the vermiform appendix is persistent in the evolutionary lineage of some mammals and can perform a few rudimentary, but handy functions. It’s original role was that of a fermentation chamber where tough to digest food can be broken down further. And it’s also a reservoir of useful bacteria that can re-colonize our guts after an excessive purging caused by a certain type of intestinal distress.
PZ Myers thoroughly analyzed this paper both for its constant “Darwin was wrong” memes used for sensationalistic PR and for its scientific merits, which are actually plentiful. But his most important point is this…
As for the argument that one function of the appendix that is significant in modern human populations is as a bacterial reservoir for recovery of gut flora after losses due to disease, that seems entirely reasonable. However, the fact that the appendix has an incidental function that can be useful to individuals in specific circumstances does not mean that the appendix isn’t a vestigial organ, nor does it necessarily mean that its retention has been selected for.
That some modern human populations have significant mortality from diarrheal symptoms (from cholera, for instance) seems to me to be a relatively trivial factor in a study that shows persistence of the appendix over many tens of millions of years, especially when no evidence of differential survival by individuals having or lacking an appendix is known.
In other words, just because the appendix might have some function which can come in handy when it’s there, doesn’t make it that much more important since people who get one removed go on to live healthy and happy lives as far as all our medical data shows us. It’s not essential and the fact that it persisted nevertheless is more of a testimony to the randomness and redundancy of how our bodies are arranged than anything else. Why else would we have organs that we could do just fine without?
The speculations about some of the appendix’s functions were around for a while and there have been plenty of creationists who used them to try and disprove that it was a vestigial organ. And they’re bound to do the same with this paper. However, all they’ll prove is that they’re easily caught up in the hype and don’t actually bother to read the paper or its analyses.
