Study: Teeth were not originally made for chewing

Researchers have discovered that teeth could come from sensory organs from 500 million years ago, informs AFP. The sensitivity of human teeth to cold or pain - that discomfort familiar to anyone who has ever bitten into an ice cream - could have a surprising explanation: teeth would have evolved from sensory organs originally intended to detect dangers in the aquatic environment, not for chewing. This is the conclusion of a new study published in the prestigious journal Nature.

• Teeth, a legacy of sensory "antennae"

The study, carried out by a team from the University of Chicago, starts from the hypothesis that the ancestors of teeth - odontodes - appeared not in the mouth, but on the skin of the first fish, about 500 million years ago. And not for chewing, but for feeling. "A toothache is actually an ancient sensory feature that probably helped our aquatic ancestors survive," explains Yara Haridy, a paleontologist and lead author of the study.

• Sharks and catfish offer valuable clues

Even today, aquatic animals such as sharks, catfish and rays have small tooth-like structures on their skin that resemble teeth. Experiments by the researchers have shown that these structures contain nerves and are capable of sensing stimuli in the water-a sign that their original function was sensory, not feeding. "It's striking how closely the odontodes of these fossilized fish resemble the sensory organs of arthropods such as crabs or spiders," says Haridy. Initially, these odontodes formed a sensory shield, providing protection, but also the ability to detect temperature, vibrations or water movement - crucial skills in an environment full of predators. "Being able to perceive the properties of the water around you was essential for survival," emphasizes Professor Neil Shubin, co-author of the study. As aquatic vertebrates evolved and developed jaws, odontodes gradually migrated to the edge of the mouth and then inside it, transforming into the teeth we know today. Therefore, the researchers explain, the current dental sensitivity - acute pain to cold, pressure or contact with sweet foods - is not a defect, but the result of an original function of perception and alertness.