Here’s a fun way to think about the timescales involved in evolution: sharks have been around so long that they have likely been around the Milky Way twice.
Just as the Earth rotates around the Sun, the Sun (with all the planets in tow) rotates around the center of the galaxy. We’re moving at around 828,000 kilometers (514,500 miles) per hour, at a distance of about 28,000 light-years from the galactic center. We’ll save you the trouble of trying to recite the exact figure of Pi from memory and performing your own calculations and reveal that this means we take around 230 million years (estimates put it somewhere between 225 to 250 million Earth years) to complete an orbit around the galactic center of the Milky Way.
That’s an unfathomable amount of time. To make it even more unfathomable (or possibly less, we can’t quite decide) that means sharks, which evolved around 450 million years ago, have hitched a lift on our planet around the galaxy twice. To put it another more flattering way, they are around two galactic years old.
A lot has changed on Earth in those two galactic years. Not to sound like a hack comedian attempting a “yo momma” joke, but sharks are so old they evolved before trees, which first arrived on Earth around 390 million years ago. While sharks changed but ultimately still carried on being sharks, the first dinosaurs evolved from lizards and enjoyed a cool 165 million years before being wiped out.
Sharks continued to not get wiped out during another four extinction events, likely thanks to their diversity.
“I think it is safe to say that it is partly because sharks are able to exploit different parts of the water column – from deep, dark oceans to shallow seas, and even river systems,” Emma Bernard, a curator of fossil fish at the Natural History Museum said in a piece for the museum. “They eat a wide variety of food, such as plankton, fish, crabs, seals and whales. This diversity means that sharks as a group are more likely to survive if things in the oceans change.”
During this time, if they’d taken the time to create telescopes as they zipped around the galaxy, they’d have seen the rings of Saturn be created.
Source Link: Sharks Are So Old They've Been Around The Galaxy Twice (So Far)