Friday, June 12, 2009

Evolution Right Before My Eyes

I went diving today, and saw an amazing creature I'd never heard of before, called a guitarfish. Here is a picture of one, taken from wikipedia:

As you can see, it's like the missing link between sharks and rays, except it isn't missing. It looks like a shark that's starting to evolve into a ray. The back end looks like a shark, but the front end is somewhat flattened and spread out like a ray, but not as much as a ray. It swims along the bottom like a stingray. Like sharks and rays, it is a cartilaginous fish, which has cartilage instead of bones. For comparison, here are pictures of a shark (also from wikipedia), a guitarfish and a stingray (my picture).

(People get so many misconceptions about evolution, I should point out that it's not like one is currently evolving into the other. The initial cartilaginous fish was probably more shark-like rather than flattened, and the flattened shape evolved out of that. An intermediate form didn't go extinct, but survives today as guitarfish. There are even some skates (a type of ray) with tails intermediate in form between guitarfish and stingrays.

I should also point out that the reason this creature seems amazing to me is because I hadn't known of it before. If I'd never known about salamanders, I would have found them equally amazing, the link between fish and lizards. "They start out like a fish, and end up like a lizard -- wow!", I would have said.)

I'd love to take a religious fundamentalist and drag them down to the bottom to show a guitarfish to them. Preferably without them having any scuba gear on. So they would drown. Because I know they wouldn't change their mind no matter what I showed them, and it would be easier than strangling them. :-)

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