Sharks are older than trees, there are more than 500 kinds of them, and almost none of them are interested in people: the biggest shark of all eats creatures smaller than a grain of rice.
The oldest teeth that definitely belong to a shark are about 410 million years old, which puts sharks in the sea long before the first forests grew on land. Most sharks are smaller than a child, live in deep water and would swim away from you. The animals in real trouble are the sharks themselves: fishing kills about 80 million of them every year.
- Kinds of sharkMore than 500
- Oldest shark teethAbout 410 million years
- Biggest shark ever measured12.65 m (41.5 ft)
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Sharks are older than trees
Sharks have been swimming for a very long time. The oldest teeth that scientists agree came from a shark are about 410 million years old. The oldest tree we have ever dug up is around 385 million years old, so sharks were already hunting before anything woody was growing on land. Dinosaurs turned up much later, and they are gone. Sharks are still here.
You may see the number 450 million written somewhere. That one comes from scattered scales, and nobody is sure yet which animal they belonged to, so it is a maybe rather than a fact. Our page on whether sharks are older than trees goes through the fossils one by one.
There are more than 500 different kinds, or species, of shark alive today, and scientists name a few new ones nearly every year. They are not all grey and pointy. Some are flat and hide in sand, some glow faintly in deep water, and some have heads shaped like a hammer. You can see the whole list on our types of sharks page.
The biggest and the smallest shark
The biggest shark is the whale shark, and it is also the biggest fish of any kind. The largest one ever measured properly with a tape was 12.65 metres long, which is about 41 feet, or roughly the length of a school bus. Scientists think even bigger ones exist, but nobody has managed to measure them.
Here is the surprising part. The largest fish in the sea eats some of the smallest animals in it. A whale shark swims along with its mouth open, or hangs upright at the surface and gulps, and tiny plankton, fish eggs and small fish get caught on filter pads inside its gills. It carries around 3,000 teeth, but they measure only about six millimetres apiece and play no role in eating.
The smallest shark we know is the dwarf lanternshark, which grows to about 21 centimetres, or roughly eight inches. A fully grown one would lie across the palm of your hand. It lives deep in the sea off the coast of South America and has little light-making spots on its belly, which probably help it hide from anything looking up at it from below.
The fastest and the slowest shark
The fastest shark is the shortfin mako. Careful measurements put its top bursts at somewhere between 45 and 70 kilometres an hour, which is about 30 to 45 miles an hour. You will sometimes read that it swims at 60 miles an hour. Nobody has ever recorded that with an instrument, so we leave it out. Even at the lower number it is quicker than almost anything else in the sea, and it can jump clear of the water when it is chasing fish. The other quick ones are listed on our page about the three fastest sharks.
The slowest is the Greenland shark, which lives in freezing water near the Arctic and cruises at less than one kilometre an hour. A person walking slowly would leave it behind. Being slow has not hurt it. Scientists used radiocarbon dating on the eye lenses of Greenland sharks and worked out that one female was somewhere around 392 years old, which makes this shark the longest-living animal with a backbone that anyone has found.
Most sharks are somewhere in the middle. Ordinary cruising speed for a shark, when it is simply going somewhere rather than hunting, is only a few kilometres an hour.
How baby sharks are born
A baby shark is called a pup, and sharks have more than one way of producing them. Some lay leathery egg cases that people find washed up on beaches and call mermaid's purses. Some keep the eggs inside the mother until they hatch, and the pups are born swimming. Some grow a connection much like the one human babies have, and feed the pups from the mother's blood.
There is a fourth way, and it is strange. A few female sharks in aquariums have produced pups with no male involved at all. It has been confirmed by genetic testing in several species. Our page on the four ways sharks reproduce explains each one.
Litter sizes vary enormously. One whale shark caught off Taiwan was carrying 304 babies at once, which is the record for any shark. At the other end, a sand tiger shark always has exactly two pups, because the first pup to grow teeth inside the mother eats the others. That sounds gruesome, and it is, but it is also why sand tigers are in trouble: two babies at a time is not many when people are catching the adults.
Are sharks dangerous to people?
Very rarely, and the numbers are worth knowing rather than guessing. The SharkSider incident database collects reports from around the world, including bites that happened while somebody was fishing or handling a shark. Across the last full decade it logged roughly 120 incidents a year, and about ten of those each year were fatal. That is out of billions of hours people spend in the sea.
Out of more than 500 species, only a handful have any real record at all. Three names cover most of the serious cases: great white, tiger shark and bull shark. Everything else on the list appears once or twice, usually because a person grabbed, fed or stood on the animal. We have a whole page on the ten least dangerous sharks.
Two things you may have heard are not true. Sharks cannot smell a drop of blood from three miles away; smell only travels as far as the current has carried it, which our page on how far sharks smell blood explains. And the idea that sharks spit people out because we taste bad has never been tested by anyone. The likelier explanation is simpler: a shark investigating something unfamiliar bites once, finds it is not the seal or fish it expected, and leaves.
Staying safe, and helping sharks
The rules that keep people safe in the sea are short. Swim where there are other people and a lifeguard. Keep out of the sea at first light and at sunset, and when the water is cloudy, because those are the hours sharks hunt and the conditions in which they mistake one shape for another. Keep away from fishing boats, piers and anyone spearfishing, since bait and struggling fish are what draw sharks in. Leave shiny jewellery on the beach. And if you are wading on a sandy bottom, shuffle your feet instead of stamping, which gives a buried shark or ray a chance to move. There is more in how to survive a shark attack.
Then there is the other side of the story, which matters more. Fishing kills about 80 million sharks a year, and better than a third of every shark and ray species assessed is now at risk of disappearing for good. Sharks grow slowly and have few pups, so they cannot replace those losses.
Children can do more about this than they think. Learning which fish came from where, not buying souvenirs made from shark parts, and telling other people the real numbers instead of the scary ones all help. Our pages on why sharks are endangered and ten easy ways to help save sharks have the rest.
Frequently asked questions
How many kinds of shark are there?
More than 500 species have been described, and scientists name a few new ones nearly every year. Most are small, deep-water sharks that people never see. Fewer than ten have any meaningful record of biting a person, and three names cover most of the serious cases.
What is the biggest shark in the world?
The whale shark, which is also the largest fish of any kind. The biggest one ever measured with a tape was 12.65 metres, about 41 feet. It eats plankton and small fish by filtering them out of the water through its gills, and its 3,000 teeth play no part in feeding.
What is the smallest shark?
The dwarf lanternshark, which grows to about 21 centimetres or eight inches, small enough to fit across a hand. It lives on the deep slopes off Colombia and Venezuela and carries light-producing spots along its belly. No incident anywhere has ever involved one, which is hardly a surprise at that size.
How fast can a shark swim?
The shortfin mako is the fastest, with measured bursts of about 45 to 70 kilometres an hour, or 30 to 45 miles an hour. The Greenland shark is the slowest, cruising at under one kilometre an hour. Most sharks travel at only a few kilometres an hour when they are not hunting.
How often do sharks bite people?
The SharkSider database recorded roughly 120 incidents a year worldwide across the last full decade, including bites that happened while people were fishing or handling sharks, and about ten deaths a year. Compared with the number of people who swim in the sea, that is a very small number.
What is a baby shark called?
A pup. Sharks produce them in three main ways: laying leathery egg cases, hatching eggs inside the mother, or growing a connection like a placenta and feeding the pups from the blood. A few females in aquariums have also produced pups without any male involved at all.
Do sharks really smell blood from miles away?
No. A shark's sense of smell is excellent, but a scent can only reach it if the current has carried it there. In still water it travels almost nowhere. The three-mile claim that appears in films and books has never been supported by any measurement of how sharks actually find food.
Are sharks in danger?
Yes, far more than people are. Fishing kills roughly 80 million sharks a year, for fins, for meat and by accident in nets set for other fish. Better than a third of the shark and ray species assessed are now classed as threatened with extinction, and because sharks grow slowly and have few pups, recovery takes decades.
References
A small team focused on researching sharks and making marine biology easy to understand. Every page is reviewed against current species records and the SharkSider attack database, and updated when new incidents or research appear.
Published March 3, 2015 · Last updated September 23, 2026 · Filed under Cool Shark Facts.
