Wednesday, July 30, 2008


I just watched the History Channel's program on the evolution of eyes. Overall it was pretty meh, but there were a couple of interesting parts.
ETA: I didn't liveblog it or take notes, so there are things I forgot. Memory is fallible. I'm human.

My favorite was in the first segment -- the experiments on the jellyfish in the tank. The researchers got a jellyfish with primitive eyespots and shone different colors of light into its tank to see how it reacted. Green light made it "relax", stop swimming, and sink to the bottom of the tank. Purple light made it start swimming really fast, and for some reason it shortened up its tentacles by a factor of 2 or 3. How do they do that? And why do they do that? Is it for speed (shorter tentacles = more drag)?

I was interrupted by a phone call and missed most of the segment on trilobite eyes. My brother, who was watching, informs me that trilobite eyes are made of calcite. Huh.

The segment on the tapetum lucidum (shiny layer in the back of some nocturnal predators' eyes that makes them look all glowy and creepy) was quite good, relative to the other sections. Not so much with the ferocious dinosaur predation or the "T3H STRUGGLE FOR SURVIVAL ZOMGZ", lots of nice creepy glowy-eyed panther shots.

Dragonflies apparently have tens of thousands of lenses in their compound eyes, and have a visual "processing speed" (define please??) ~5x that of humans. Badass.

There was a weirdly long segment of dinosaur obsession. Whenever I see this kind of sensationalism it makes me sad, but I suppose it's only to be expected anymore. The epic, ceaseless struggle for survival! Eat or be eaten! And I imagine, sometime when this episode was being planned, some editor was all "we gotta have dinosaurs in all our nature programs!". Far too much time spent on dinosaurs in a program about eyes. They should have cut this by 90% and spliced in some material on cephalopod eyes, or the design flaws in the human eye, or more than perfunctory detail on intermediate stages between "patch of light-sensitive cells" and "fully evolved eyeball". All of which were either mentioned briefly or omitted altogether.

The other thing that really bothered me about this program was some of the things they felt necessary to explain: Humans are mammals. Vertebrates include reptiles, mammals, and birds. How can kids past kindergarten not know this stuff?

Also -- ok, I would really have liked to see a mention of how wildly different species use a lot of the same genes to control development, and how this interacts with (convergent) (eye) evolution, but this is a ridiculous thing to hope for, given the level of the program. Why are they showing kids-level programming at 10 pm?

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