Older than the dinosaurs and ecologically vital, sharks deserve more than our fear.
Long portrayed in pop culture as remorseless people-killers, sharks in reality are no Hollywood monsters. Sharks are a diverse group of mostly predatory fish, including the largest living fish, with skeletons made of cartilage. They have plied the seas since before the dinosaurs lived and play vital ecosystem roles.
Sharks’ long evolutionary history includes reaching tremendous size, when one of Earth’s biggest apex predators, the gigantic megalodon (Otodus megalodon), hunted the oceans.
At high risk of extinction, these marine creatures as a group face far more dangers from humans than any surfer does from a great white shark.
All sharks belong to the subclass of fish called elasmobranchs, along with skates and rays. Lacking bones, elasmobranch skeletons consist of the hard but flexible material cartilage, which is also found in your ears and nose, according to the Smithsonian(opens in new tab).
Because cartilage skeletons rarely fossilize, establishing the natural history of sharks can pose a challenge, according to the American Museum of Natural History(opens in new tab) in New York City. But sharks’ impressive teeth, along with scales, leave enough of a record to estimate that the animals first evolved more 450 million years ago, according to the Natural History Museum(opens in new tab) in London.
That timeline means sharks prowled the primordial seas around 200 million years before the first dinosaurs, even predating the first forests(opens in new tab), which didn’t appear until 385 million years ago, Live Science previously reported. Over those eons, sharks survived “the big five mass extinctions.” They even enjoyed a “Golden Age” beginning around 360 million years ago, when a tremendous global die-off claimed many fish, leaving sharks to dominate — and proliferate into new species, according to London’s Natural History Museum(opens in new tab).
Sharks have evolved into roughly 500 species alive today, according to the Shark Foundation(opens in new tab), and they range widely in size, shape and even color. You could fit the smallest living shark in your pocket; the dwarf lantern shark (Etmopterus perryi) spans just 3 inches (8 centimeters), according to the Smithsonian(opens in new tab). Sharks also hold the titles of both largest fish and largest predatory fish. The “gentle giant” whale shark (Rhincodon typus) can stretch to nearly 40 feet (12 meters) long, eclipsing a full-size school bus, the World Wildlife Fund(opens in new tab) says.
You likely know the largest predatory fish, great whites, from their extensive film credits, most prominently 1975’s “Jaws.” Female great whites grow bigger, at an average length of 15 to 16 feet (4.6 to 4.9 m), while males reach 11 to 13 feet (3.4 to 4 m). The largest great white ever, nicknamed Deep Blue, spanned 20 feet, Live Science previously reported. Using computer modeling techniques, a 2008 study in the Journal of Zoology(opens in new tab) estimated that great whites exert a bite force of up to 2 tons (1.8 metric tons), or more than three times that of a large African lion (Panthera leo leo).
Prehistory’s biggest shark dwarfed even Steven Spielberg’s killer fish. Megalodon, which swam the ancient seas from about 23 million to 4 million years ago, grew up to 65 feet (20 m) long, according to 2021 re-estimates based on the creature’s teeth published in the journal Palaeontologia Electronica(opens in new tab). Megalodon has also gotten the pop culture treatment, starring in a fake documentary that suggested the behemoth fish survived today. But rest assured: Scientists insist there’s no evidence for that.
Shark species also vary widely in shape, from the built-for-speed torpedo design of great whites to the long, tooth-lined snouts of saw sharks. The odd-looking goblin shark makes a distinct impression with its flabby body and shovel-like snout set above a retractable mouth, according to the Australian Museum(opens in new tab). Shark skin paints a rainbow, too. Those little lantern sharks dress in a conservative dark brown but glam things up with light-emitting organs, according to the Smithsonian(opens in new tab). One deep-sea goblin shark found by the Australian Museum(opens in new tab) in 2015 sported a bright pink hue, while carpet sharks get their name from ornate skin patterns, according to the Smithsonian.
Scientists uncover newfound species yearly, according to the World Wildlife Fund(opens in new tab). In 2021, the so-called Godzilla shark — an ancient, 6.7-foot-long (2 m) beast discovered in 2013 and so nicknamed because of its reptilian spines — got a new name: Hoffman’s dragon shark (Dracopristis hoffmanorum). Also in 2021, researchers discovered the 6-foot (1.5 m) kitefin shark (Dalatias licha), the largest glow-in-the dark shark — in fact, the largest glowing vertebrate — ever found, as reported in the journal Frontiers in Marine Science(opens in new tab).