In honor of the world premier of David Shiffman’s first major motion picture, “Four things everyone needs to know about sharks,” we are proud to repost our original response to the article, “Sharks are sub-par, at best.” Enjoy!
For too long have I sat idly by as my co-blogger has waxed poetic on the glories of sharks. How great they are as predators, how perfectly they’ve evolved. They’re ancient, pre-historic, haven’t changed in millions of years. They’re the ultimate predator, and champion in the ocean. Unchallenged, unmatched, awesome. A wonder of evolution.
It’s time to clear up some of those -other- myths about sharks.
1. Sharks are ancient creatures that have lived unchanged for millions of years.
While technically true that sub-class Elasmobranchii has been around for hundreds of millions of years, modern sharks are, well, modern. They’ve been evolving for exactly as much time as just about everything else currently alive. And they are far from unchanged. Modern sharks, though they may resemble some older models (just like modern lemurs resemble Ida), are much different beasts then their Silurian cousins. Ancient sharks occured in a diversity of forms, back when they actually dominated the ocean. These modern sharks are just the scruffy leftovers.
The other part of this equation is that while some elasmobranchs retained their primitive characteristics through present time, the most successful ones did not. These are the elsmobranchs that are the common ancestors of modern bony fish, modern tetrapods, modern primates. Yeah, some sharks stayed sharks, but the common ancestor of nearly all vertebrates was some kind of elasmobranch.
2. Sharks are marvels of evolution, perfectly adapted to their environment.
Well, no, not really. Not at all actually. As with everything that evolves, sharks are a fairly sub-optimal design. They’re bad at regulating heat, removing waste, they’re very energy inefficient. But much much worse than that, modern sharks are bad at evolution. They are slow reproducers with small brood sizes. There is low genetic variability between generations. All that builds up to the fact that sharks can’t quickly adapt to changes in their environment. Mammals can. Arthropods do it better than anything. Sharks benefit from a wide range of tolerances, but populations can’t survive rapid environmental change, like, say, ocean acidification or over-fishing. But that’s all just semantics, because there’s no such thing as a perfect predator, just one that’s ideal for the environment it’s in. And sharks are pretty good, but not perfect.
3. Sharks can smell a drop of blood miles away.
Ok, this on has always seemed pretty silly, and has nothing to do with sharks and everything to do with how little people tend to know about chemistry or physiology. You can’t smell a molecule of anything from any distance. You can only detect molecules that are sitting on whatever sensor you use to sense them.
Sharks can detect an incredibly dilute molecule in the water. But if you drop a bucket of chum overboard, they’re not going to immediately know several miles away, you’ll have to wait until the chemical cues reach them. That’s not very impressive. Most animals have a range of chemical cues they can pick up on in incredibly low dilutions.
4. Sharks are the ultimate predator in the ocean.
There’s a whole mess of different ways to be a predator, and sharks are fairly dull. They don’t have venom, adaptive camouflage, they don’t regularly fight giant squid or snipe insects out of the air. They don’t have sonar, radar, infrared. All they’ve got going for them is their electrosensitivity, which puts them on par with that most fearsome of creatures, the duck-billed platypus. Oh noes! Not the platypus, I’m quaking in my wetsuit.
Oh, wait, platypuses have venom. I guess sharks lose to them, too.
~Southern Fried Scientist