Tuesday, March 25, 2008

Do fish have knees?

Well, some of them do. We have knees, and since you could call us fish, then some fish have knees.

I was thinking about fish and knees while walking in the park this afternoon. It's a beautiful day in New Jersey -- clear blue skies, plenty of sunshine -- so I went for a walk. Towards the end, though, my knees started to hurt. I don't have good knees. I have unhappy knees. However, my unhappy knees made me think about why we have the knees that we have in the first place, and that reminded me of a great article I just read recently. This article, which was the cover story in Natural History Magazine in February, is by Neil Shubin, a prominent paleontologist whose greatest hit is Tiktaalik, a recently-discovered early tetrapod.

Along with addressing things like hiccups and hernias, Dr. Shubin briefly discusses the reason we have knees, namely, it was the best we could do with what our fish ancestors gave us. Incidentally, I think bad knees might be sufficient proof to stop the whole intelligent design crew in its tracks; unless we are to assume that our designer was not only intelligent but malicious, why would we have knees built the way they are, easily damaged and held together by little more than a few strips of connective tissue?

But hey, maybe that's just because I have bad knees.

I also love observing, as I walk, that without thinking about it at all, I swing my arms in a characteristically tetrapod way -- that is, the right arm goes forward when I step with the left. Whenever I think about that, I a) fall over, because I immediately get my brain involved in a central pattern generator, which is bad and b) think about videos of coelacanths. Unfortunately, I can't find one to post right now... maybe later. But they too swing their fins in an opposing pattern like that.

Anyway, read Dr. Shubin's article, it's really interesting! I'm thinking about reading his book over the summer when I have more time to think about vertebrates again.

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