To study how fish fared after this devastating extinction, the University of Pennsylvania's Lauren Sallen (along with Andrew K. Galimberti, now a graduate student at the University of Maine) studied 1,120 fish fossils dating back 419 to 323 million years ago. She found that the ancient fish had been increasing in size over time — which is to be expected — but that body size plummeted after 97 percent of species were wiped out.
“Some large species hung on, but most eventually died out,” Sallan said in a statement. Before the extinction, some fish had grown to be as big as school buses. But in the unstable ecosystem of a post-mass-extinction ocean, only small fish — ones that could reproduce quickly and survive on less food — could thrive.
That means an ocean full of enormous sea monsters gave way to an ocean full of sardine-like critters. “[T]he end result is an ocean in which most sharks are less than a meter and most fishes and tetrapods are less than 10 centimeters, which is extremely tiny. Yet these are the ancestors of everything that dominates from then on, including humans," Sallan said.
There's a very good reason to look into these devastating extinctions of the distant past: Many scientists believe that Earth is on the verge of a sixth mass extinction — one caused by human activity.
It's not like this is the first indication that a modern mass extinction would be, um, not great for the planet. But it's another reminder that the global ecosystem can't bounce back from such massive blows quickly enough for humans to be unaffected. At the very least, Sallan says in the video above, "sushi plates might get much smaller."