Sharks Weren't Always This Scary

Take a seat, shark denialists. Turns out sharks today are probably scarier than they've ever been before in history, because evolution has made sharks better at all things terrifying. Sharks in the past were scrawny piranhas compared to the great undulating beasts that stalk the waters today, apparently, and it's all based on a new fossil researchers found.

You may remember learning back in school that sharks are a throwback to a different era — the shark, in other words, is a "living fossil" that lets researchers look into the past. With the discovery of the new fossil, scientists are rethinking that idea. The 325 million-year-old fossil still looked pretty scary, but it was markedly different than the sharks we know today. Sharks back then were more like big fish, with small teeth and shorter bodies.

The old sharks had different gills, too, which is a big change in the conventional wisdom on gill evolution (by the way, there's conventional wisdom about gill evolution. You learn something new every day!). Scientists had thought that the gill structure of sharks was a remnant of a previous era, and that fish had more evolved gills.

But because the old shark fossil's gill structure is more like that of fish, shark scientists are now thinking that fish gills are less evolved, not shark gills. If you're a science nerd, that makes your fish dissection perfect for next week's #tbt.

A researcher at Sweden's Uppsala University told NPR's All Things Considered that the fossil, which looked like nothing more than a big brown rock, could really change the way scientists think of sharks.

There's been this very, very deeply established idea of sharks as being primitive, as being unchanging. ...We have to be very, very careful with the idea of living fossils. And it's something that researchers in this field have more and more moved away from.