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Here’s what you’ll learn when you read this story:
Sharks are older than a surprising amount of things, both on Earth and in the rest of the universe.
While sharks have seen evolutionary changes in the 450 million years they have been around, their body plans have held up for eons because they have been so successful.
The oldest known individual vertebrate is a shark that has probably reached its 400th birthday by now.
To say sharks are ancient is a behemoth of an understatement. They evolved around 450 million years ago, before Saturn’s rings, the Pleiades cluster, too many exoplanets to name, and the North Star came into existence. During the stretch of astronomical time sharks have existed, the Solar System has fully orbited the core of the Milky Way twice.
Sharks are thought to have emerged late during the Ordovician period—an epoch during which the continents that formed the supercontinent Gondwana would begin to shift into what would become Pangaea. During that era, Earth was an almost alien planet. The seas were rife with bizarre forms of life such as trilobites, crinoids, moss-like bryozoans, shelled cephalopods known as ellesmocerids, and conodonts (the ancestors of hagfish). Land plants had just begun to appear after transitioning out of water. Trees (in the form of progynmosperms) would eventually come around, beginning to grow anywhere from 30 to 100 million years after sharks came into existence, but flowering plants would not bloom for another 230 million years.
Even dinosaurs only began to roam Earth during the Triassic, about 243 million years ago—they evolved well after sharks and went extinct just a few hundred million years later. Us humans have only been wandering the planet for around 300,000 years, making sharks over a thousand times older than us. These toothy elasmobranchs have also survived mass extinction after mass extinction—all five of them.
So… how did they do it? How did sharks manage to remain so unchanged and thriving through destructions of apocalyptic proportions? The End-Permian Mass Extinction, or The Great Dying, took out 96% of marine life.
It turns out, sharks are highly adaptable—enough so that it saved them from annihilation by everything from sulfurous volcanic gases that acidified the oceans to the massive Chixculub asteroid impact that ended non-avian dinosaurs. Sharks lurk in the dark depths, the shallows, and everywhere in between. When an immense amount of oxygen was choked out of the oceans towards the end of the Permian period, they were able to easily move to more oxygenated areas and occupy different niches. If one species of prey died out, sharks would just hunt another.
While sharks have certainly evolved over the years, the prototype of the body plan that would give them an edge was established early on. Their skeletons are made entirely of cartilage and much lighter than bone, giving them more buoyancy and requiring less energy from them to swim than bony fish (which are more prone to sinking and need to expend more energy to stay afloat). Shark skin is protected by dermal denticles—overlapping hard plates that reduce drag to facilitate swimming. Those iconic jaws and teeth are assets that allow sharks to devour prey larger than they are so as to not need to refuel as often.
Sharks aren’t alone in their ancient-ness, however. There are other creatures that have not changed too drastically over eons. Crocodilians, for instance, haven’t seen much change in over 200 million years, with fossils from their earliest periods of existence showing remarkable morphological similarities to species that exist today. The tuatara—a reptile that is often understandably mistaken for a lizard—looks much like it did 190 million years ago. Coelacanths and nautiluses are both leftovers from prehistoric seas. If a body plan continues to be successful, it might still evolve, but it will remain mostly the same.
Not only have sharks as a group been around longer than stars and planets, but some individual species live unbelievably long lives. The oldest known Greenland shark had already lived almost 400 years when it was studied in 2016. If it was walking on land, it would remember Shakespeare.
Hey—if it ain’t broke, don’t fix it.
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