Biology
Why Sharks Never Run Out of Teeth
Quick fact
A single shark can grow and shed over 30,000 teeth in its lifetime, with some species replacing a tooth every 8–10 days.
Why this is interesting
You've probably heard that sharks lose thousands of teeth, but have you ever wondered how they never end up toothless?
Read the full explanation
Understanding Why Sharks Never Run Out of Teeth
Sharks don't have a single set of permanent teeth like humans. Instead, they have multiple rows of teeth arranged in their jaws—often 5 to 15 rows deep. The front row is the functional row used for biting. Behind it, rows of developing teeth sit in a trough, waiting to move forward. When a front tooth breaks, falls out, or wears down, a tooth from the next row rotates forward to replace it, much like a conveyor belt. This process continues throughout the shark's life, ensuring a steady supply of sharp teeth.
A deeper explanation
This process is called polyphyodonty, meaning multiple generations of teeth. Sharks have a specialized tissue called the dental lamina that continuously produces new tooth buds. Each tooth develops inside a protective sac, then gradually moves forward along the jaw. The replacement is triggered by the loss or wear of the functional tooth. This mechanism is highly efficient: teeth are replaced quickly, often within days, so sharks are never without a full set. Polyphyodonty is an evolutionary advantage for predators that rely on sharp teeth to catch and consume prey, compensating for the high rate of tooth damage in a marine environment. Unlike humans (diphyodonts) who have only two sets, sharks are lifelong tooth factories.