Why Haven’t Sharks Evolved?


Why Haven't Sharks Evolved?

Sharks are older than dinosaurs. They’ve stood the test of time and are almost exactly the same as they were all those millions of years ago. It begs the question: why haven’t sharks evolved?

Sharks have evolved, it just doesn’t really seem like it. Sharks have no known predators so they dominate their ocean landscape. As long as their dominion remains the same, they have no reason to adapt in a large way.

Let’s take a closer look at why sharks are the true kings of their habitat and how that notion might apply to us as well.

Examples of Shark Evolution

Just like in my article all about crocodile evolution, the easiest way to see the difference between the ancient sharks and more modern sharks is in their size.

The biggest shark in the world right now is the whale shark. Some whale sharks have been known to reach lengths of about 13m (just over 40 feet). Not too bad!

The biggest prehistoric sharks, however, grew to sizes of nearly 24m (over 70 feet)!

That’s almost double the size of our largest modern day sharks.

Example Shark Sizes
  • Helicoprion – Lived about 290 – 250 million years ago and was about 9m (close to 30 feet)
  • Megalodon – Lived about 26 – 2.3 million years ago and was about 19m average (close to 60 feet). The name is Greek for “big tooth” because of their huge 7 inch (18 cm) long teeth. Yikes!
  • Great White Shark – Has been around for millions of years (scientists are thinking around 6 million or less) and they can reach sizes of about 8m (around 24 feet). By all means not the biggest shark we have today, but is one of the most vicious. It’s the largest of our modern predatory sharks. These are the ones that haunt our dreams and give us movies like Jaws that make us afraid of water!

Sharks have evolved their size based on prey and environments throughout the years. They were bigger when there was bigger prey.

What I find interesting is how nature tends to strike a balance between carnivores and herbivores. As herbivores get bigger so do carnivores.

This is most evident when you look at how crazy big some of the dinosaurs got in the Jurassic period!

One other major example of shark evolution lies in their brain size. Some of the early sharks some 400 million years ago had way smaller brains than the sharks of today.

How Sharks Show a Different Side of Evolution

Sharks, and crocodiles, show how evolution actually truly works. Evolution is nature’s way of sifting through all of the earth’s species and finding the ones that adapt better than others.

Sharks are the best evolved for their environment and have been for millions of years.

The only evolution we’ll likely see in the future with these apex predators is their size and intelligence. Just like how they got bigger through the different dinosaur periods, we might see sharks get larger again if their prey grows in size and population.

Sharks could get smaller, as well. It really could go either way.

What Sharks Evolved From

Sharks basically evolved from fish.

The first fish appeared about 510 million years ago. They were small and jawless, not exactly prime elements to be survivors.

Sharks clearly had an evolutionary edge when they came onto the scene about 400 million years ago. Their teeth and jaws gave way to new predatory ambition and sharks took over the oceans. They’ve stayed on top ever since!

Just like crocodiles, sharks did not evolve from dinosaurs. They’re all completely different species from each other, evolving in different ways.

How Sharks Survived the Dinosaur Extinction

Around 65 million years ago, scientists believe a giant meteor came and struck the earth in the Gulf of Mexico.

One major theory is that the area was incredibly rich in oil and because of that it caused excess amounts of carbon dioxide and fumes to flood the atmosphere, blocking out the sun and disturbing photo synthesis in the vegetation.

I wrote an entire article about fossil fuels and how oil may have helped kill the dinosaurs. Check it out!

The dinosaurs perished, but there were some species that survived and thrived! Two of the major ones that I’ve discussed are crocodiles and sharks.

In my article about crocodiles, I mention that the reason they might have survived is because they were cold-blooded and required a lot less energy from feeding.

Guess what? Sharks are also cold-blooded!

It seems safe to say that the reason that they survived is because they were cold-blooded.

Interesting piece of trivia: sharks have actually survived 4 of the 5 mass extinctions in Earth’s history! Way to go, scary killer ocean beasts!

Related Questions

Do sharks come from dinosaurs? Sharks come from fish ancestry that is different than dinosaur heritage. It’s suggested that all life comes from marine life, but the difference is sharks come from a line of cartilagenous fish whereas the dinosaurs come from bony fish instead.

Are sharks primitive? Depending on the definition of primitive, yes and no. They are primitive in the sense they come from an ancient species line, but are sophisticated in the sense of evolutionary traits. They have exceptional senses of smell and also an electrosensory system that allows them to sense the muscle movements of animals in the water.

How many great white sharks are left in the world? There isn’t a definitive answer to how many sharks are left in the entire world, but several coastal countries have found there to be thousands of great whites in their vicinity. It’s probably fair to say there’s anywhere from 10,000 to 100,000 great whites in total.

Conclusion

Sharks are scary, no matter what scenario you find them in. They can rip apart prey like no tomorrow and have the swimming skill of Olympians. Not only did they exist in the prehistoric, they were also bigger. Let that visual sink in!

Aside from size differences, sharks today largely remain the same as their ancient ancestors. I guess when you’re the king of your domain there’s no need to change. Either way, don’t go in the water. Dun dun, dun dun.

Jeffrey Rank

Jeffrey Rank is a dinosaur nut that has finally embraced his love for all things prehistoric. He's seen Jurassic Park far too many times and bores his family to tears with dinosaur trivia and knowledge.

Recent Content

link to Did Dinosaurs Sleep at Night?

Did Dinosaurs Sleep at Night?

Most species on the planet sleep at night. There are, however, the odd nocturnal animals around – or people who work night shifts – that sleep during the day. It makes you wonder, though: did dinosaurs sleep at night? Most dinosaurs slept at night just like our current animal kingdom. There were some nocturnal dinosaurs […]