25 million years old and it's still sharper than your kitchen knives. Sharks evolved 420 million years ago when no animals were on land, no bugs even, just a few plants. They have no bones, no ribs, just a cartilaginous skeleton that is much lighter so they can swim quicker, it's more buoyant and they expend less energy and the amazing teeth consist of easily fossilized calcium phosphate. Incredible perfect killing machines designed by Evolution, but don't meet one in the ocean.
