PZ Myers Weighs in on the Appendix
As I posted a few days ago, a group of researchers has made some interesting claims regarding the appendix.
Not only does the appendix have functionality (namely, it provides a reservoir for healthy bacteria to hide out during digestive or intestinal issues such as diarrhea), the researchers have determined that the appendix has evolved at least two seperate times and has only recently (for humans) developed problems such as severe inflammation.
A great deal of the article references Charles Darwin and his misconceptions about the appendix. PZ Myers, never one to miss an opportunity to set the record straight, has weighed in over the weekend on the way Darwin was used throughout various articles in highlighting the research:
Charles Darwin is dead. Your research can't be very cogent if your approach to drum up interest is to dig up a 120-year-old corpse and kick it around; is there anyone alive who disagrees with you who can put up a more informative and entertaining struggle? What this does is pick this one fellow as a symbol of the whole edifice of evolutionary theory, which has the advantage of making one's work seem very, very important (even if one is stacking the deck to do it), but has the disadvantage of giving every creationist on the planet something to masturbate over, and they're icky enough without your help.
It's also annoying. Charles Darwin was wrong about many things — I'll even give an example at the end of this article — and it's part of the nature of science that everyone's work will be revised and refined over time, and some of us will even be shown to be completely wrong. It's rather unseemly to collect a lot of data that Darwin did not have, run it through PAUP 4.0 on a fast computer, map the data onto a molecular consensus phylogeny, and cackle gleefully over discovering something Darwin did not know. Really, it doesn't make you a better scientist than Darwin.
To make it even worse, people who do this can't even make the corpse-fight a fair fight — they have to stuff the pathetic dead body with straw. In this case, they're padding Darwin's investment in the appendix a fair amount. They cite one work by Darwin, The Descent of Man, which mentions this issue. He wrote one whole paragraph on the topic, and here it is, in its entirety; it was presented briefly as part of a long list of human rudimentary structures, such as wisdom teeth, muscles of the ear, and the semilunar fold of the eye.
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 is extremely long in many of the lower vegetable-feeding mammals. In the marsupial koala it is actually more than thrice as long as the whole body. (46. Owen, 'Anatomy of Vertebrates,' vol. iii. pp. 416, 434, 441.) It is sometimes produced into a long gradually-tapering point, and is sometimes constricted in parts. 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. That this appendage is a rudiment, we may infer from its small size, and from the evidence which Prof. Canestrini (47. 'Annuario della Soc. d. Nat.' Modena, 1867, p. 94.) has collected of its variability in man. It is occasionally quite absent, or again is largely developed. The passage is sometimes completely closed for half or two-thirds of its length, with the terminal part consisting of a flattened solid expansion. In the orang this appendage is long and convoluted: in man it arises from the end of the short caecum, and is commonly from four to five inches in length, being only about the third of an inch in diameter. 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. (48. M. C. Martins ("De l'Unite Organique," in 'Revue des Deux Mondes,' June 15, 1862, p. 16) and Haeckel ('Generelle Morphologie,' B. ii. s. 278), have both remarked on the singular fact of this rudiment sometimes causing death.)
Note why Darwin classed this appendage as vestigial: because it is greatly reduced compared to the homologous organs in non-human relatives, and because it currently exhibits a great range of variation, which is apparently non-functional. These are criteria which the paper in question does not refute at all. Darwin does say that the appendix is "useless", and the paper will show some evidence that that is wrong. It's also irrelevant.
The reason why it is irrelevant is that the presence of some function is not part of the definition of a vestigial or rudimentary organ — Darwin obligingly concedes that evolution will salvage some utility out of organs with little retention of their original function, but which are present as a consequence of contingency....
If a portion of the gut, a digestive organ, is diminished in size such that it no longer contributes to the primary function of the organ, but does retain a secondary function, such as assisting in immunity, or as the authors of the recent paper will argue, in acting as a reservoir of bacteria for recolonizing the gut, then it is still a vestigial organ. It has lost much of its ancestral function.
I do not understand why this is so hard for so many people to comprehend. Biology is plastic and opportunistic. Accidents of history will always still be incorporated into the whole of the organism; we make do, or we die. Just because something is does not mean that the entirety of its nature is the product of selection.
