Mathematics
Why Do Sharks Never Run Out of Teeth?
Quick fact
Some sharks can lose and replace up to 30,000 teeth in a 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 over their lifetime. But how do they keep eating without ever going toothless?
Read the full explanation
Understanding Why Do Sharks Never Run Out of Teeth?
Unlike humans who have one set of baby teeth and one set of adult teeth, sharks are polyphyodont—they continuously grow new teeth throughout their lives. Their teeth are not rooted in a jawbone like ours; instead, they are embedded in the skin of their gums. Most sharks have multiple rows of teeth (up to 15 rows) that work like a conveyor belt: the front row does the biting, and when a tooth falls out or wears down, a new tooth from the row behind moves forward to take its place. This process is constant, so sharks never run out of functional teeth.
A deeper explanation
The mechanism behind this endless supply is the dental lamina, a band of epithelial tissue in the shark's jaw that continuously produces tooth buds. Each tooth is formed within a pocket of skin and then erupts like a tiny conveyor belt. As the tooth matures, it moves forward, and the old one is shed. This adaptation evolved because shark teeth are not for chewing but for tearing prey; they often break or fall out during attacks. Replacing them quickly ensures the shark always has a sharp, effective weapon. This process is also energy-efficient—sharks don't invest in keeping teeth long-term, which would be wasted energy, given their rough lifestyle. Understanding polyphyodonty in sharks helps explain why other animals with similar tooth use, like crocodiles and some fish, also replace teeth continuously.