Saturday, September 5, 2009

A Tale of Two Fishes

Today, my wife and I were discussing, as you do, why a bunch of people that I was working with, all of whom have a solid background in biology, seemed to be incapable of describing natural selection and adaptation in language that a layperson could understand. This post is nothing at all to do with that conversation, but in reminiscing about our respective college educations the subject of Acanthostega came up. Don't ask me why, but it did.

Now, you kids may not have heard of Acanthostega, but when she-who-is-not-to-be-mentioned-by-name and I were at university this crazy little bundle of Devonian fun and games had a pretty good claim to being the hottest paleontological discovery of the century. When we started out as students, the whole world was absolutely convinced that the earliest tetrapod had five digits. Scholarly tracts soberly numbered the various fin bones of osteolepiform fish from I to V in an attempt to demonstrate homology. Then along came 8-fingered Acanthostega (not to mention 7-toed Icthyostega) and blew all this out of the water (hohoho, I made a pun!).

I guess we may have had a rather biased view of all this, as SWINTBMBN was taught by the one of the discoverers of Acantostega's polydactylous paddles, Jenny Clack, while at Cambridge, and we both went on to work with another of the discoverers, Per Ahlberg, at Oxford. Nonetheless, it was fair to say that across a range of disciplines, from genetics to developmental biology, to anatomy and evolutionary biology, little Acanthostega gunnari blew open paradigms left, right, and center. But talk to the kids nowadays and what do you hear? Tiktaalik, Tiktaalik, Tiktaalik, that's what.

So what is with this Tiktaalik guy? OK, as intermediates go it's pretty cool: terapod ankle bones but fishy fin rays instead of toes; gills and lungs; fishy scales, but a mobile tetrapod neck. It's about as intermediate you can get. It most certainly helps fill in a pretty significant gap in the fossil record. But rewriting your basic biology textbook? I think not.

Of course, it's also true that like all good fossils these days (cf that other "Find of the Century," Ida the Monkey) Tiktaalik comes complete with press coverage, a book deal, and a music video. "Grace" the Acanthostega was found over 20 years ago, when the best you could hope for was that one of your mates would write a "News and Views" piece in Nature and you'd get a couple of minutes with John Craven on Newsround. But maybe there's something more sinister at work. As SWINTBMBN pointed out, there were no Americans involved in the discovery of Acanthostega's eight toes....

Of course, I immediately remonstrated with her, reminding her that the USA is famed for the interest that it takes in the achievements of other countries and their people.

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