Thursday, October 15, 2009

Of Pterosaur Modularity

If CNN is to be believed -- and mind you, it is not, or only within strict limits -- easily-surprised scientists have found fossils of a transitional form of flying dinosaur:

The fossils were found in northeast China earlier this year, embedded in rock dating back 160 million years, and have been called "Darwinopterus" after the renowned naturalist Charles Darwin.

The creature's discovery has astounded scientists because their age puts them within two recognized groups of pterodactyls -- primitive long-tailed forms and advanced short-tail forms -- and they display characteristics of both.

The combination of features indicates that the primitive pterodactyls evolved relatively quickly, and that certain groups of features changed at the same time.

Traditional evolutionary theory suggests that one feature -- a tail for instance -- would slowly evolve over time.

"Darwinopterus came as quite a shock to us," said David Unwin, from the University of Leicester's School of Museum Studies ... [emphasis mine]
Yes, scientists have discovered a fantastic new species of pterosaur; but no, this stuff about "traditional evolutionary theory" demanding that creatures slowly evolve over time (whatever slowly means) is hogwash. The pace of evolutionary change is a source of lively scientific interest and research, but suffice to say there is no "tradition" that establishes a "slowly" against which any given discovered instance of "not-slowly" will astound scientists.

David Unwin's "shock" and "astoundedness" is placed in more complete, less dramatic context in the hands of Darren Naish's delicious geek-out on the discovery, which includes more genuine pterosaur science than any ten CNN butt-scratchings:
So it's almost as if the head and neck were evolving at different rates from the rest of the body: in other words, Darwinopterus looks like a classic case of 'mosaic evolution' or modularity (hence the species name). This much-discussed evolutionary phenomenon has been considered controversial, in part due to a lack of good examples: Darwinopterus looks like one of the best yet discovered ... Darwinopterus lends support to the hypothesis that different segments of anatomy - the modules - can become disassociated, and then evolve at separate rates relative to one another.
There's a good deal more to be said about this discovery and of the deficiencies of CNN's reporting, but I am going to have to leave it there.

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