How do sharks keep their teeth so sharp? And why does it matter? Unlike land predators, the fish don’t have claws—they use their teeth for catching prey. If a shark’s teeth are lost or get dull with use over time, that presents a major problem to its survival. So the animals have evolved a fascinating solution to this issue.

While humans just get baby teeth and adult teeth, sharks are constantly growing chompers throughout their entire life. A set of new teeth is always developing in the predators’ jaw, and they rotate forward like a conveyer belt. In this colorized x-ray of a shark’s jaw, the teeth on the bottom are currently in use, while those on the top are in the process of growing and rotating forward. As the teeth in use are worn down and lost, replacements emerge. A single shark may go through as many as thousands of teeth in its lifetime. It can continue to hunt and eat tough-skinned prey without fear of breaking or dulling its teeth—because there will always be new ones waiting to take their place.

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