Being able to tear and chew food was a revolutionary step in the ability of species to consume energy, and sharks – as some of the earliest animals to have teeth and jaws – hold important clues for understanding the evolution of teeth throughout the natural world. Until recently, it was widely believed that shark teeth evolved from the dermal denticles that cover the animals’ bodies, eventually migrating into their mouths. However, a new study suggests that it was taste rather than touch that gave rise to modern teeth.
A research team from the University of Sheffield in the United Kingdom examined the stem cells of a shark embryo during its development and found that both teeth and taste buds develop from the same cells in the embryo’s mouth. While some animals, including humans, have taste buds on their tongues, sharks have finger-like buds that line the mouth and pharynx and are concentrated mostly on the soft tissue just behind the teeth. By tracking the development of embryonic stem cells in the shark’s mouth, the researchers established not only that these cells are the building blocks of both taste buds and teeth, but also that they hold the secret to a shark’s ability to regenerate teeth – and taste buds – throughout their life.