Friday, September 28, 2007

Why do dinosaurs have feathers?

Not having paid too much attention to dinosaurs, I was caught on the hop by the velociraptors in the Jurassic Park films. Never heard of them before.

Turns out that was cinematic largesse (so to speak). The real velociraptors were apparently only a metre high.

And now we find that they had feathers. Published a few days ago in the journal Science, Mark Norell of the American Museum of Natural History details "quill knobs" in the bones of velociraptors found in Mongolia.

Norell details a surprising number of features and habits shared between birds and velociraptors, including nests and hollow bones. (I mentioned recently that those hollows were characterised by Peter Ward as air sacs to aid respiration - breathing.)

From the tenor of the piece, it's still unclear whether the velociraptor's feathers were handed down by flying ancestors, but other functions were proposed, such as temperature control or in aiding stability while in fast motion.

Which brings me on to a significant and exciting point in evolutionary history that has been remarked on by Charles Darwin and Stephen Jay Gould in turn (and doubtless many in between):

Redundancy. The mechanism that facilitates evolutionary change: two-for-one - an organ or feature that can fulfil two functions; and one-for-two - two different organs that fulfil effectively equivalent roles.

These mechanisms permit stability and viability at a time of change: favourable mutations find favourable uses for such redundancies. More to come on this.

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