That zing in your teeth from a cold treat? Blame this ancient armored fish - NPR

The sometimes uncomfortable sensations we feel in our teeth may be an evolutionary holdover from the scaly exteriors of ancient armored fish.

That uncomfortable zing you feel when biting into ice cream or during a dental cleaning has a surprising evolutionary origin, according to a groundbreaking study published in Nature. Researchers have discovered that the sensitivity of human teeth can be traced back to sensory structures in the armored exoskeletons of ancient fish that lived approximately 465 million years ago.

"A toothache is actually an ancient sensory feature that may have helped our fishy ancestors survive!" said Dr. Yara Haridy, an evolutionary biologist at the University of Chicago and lead author of the study.

From Ancient Armor to Modern Teeth

Haridy and her team initially set out to identify the oldest vertebrate in the fossil record, focusing on dentine—the sensitive inner layer of teeth that transmits sensory information to nerves. Using high-resolution CT scans from the Advanced Photon Source at Argonne National Laboratory, they examined hundreds of fossil specimens, some tiny enough to fit on the tip of a toothpick.

What they discovered upended conventional understanding about the evolution of teeth. The researchers found that tooth-like structures called odontodes, which appeared as bumps on the external armor of ancient fish, contained dentine-filled tubules connected to nerves—suggesting they evolved primarily as sensory organs rather than for protection or feeding.

"When you think about an early animal like this, swimming around with armor on it, it needs to sense the world," explained Dr. Neil Shubin, senior author of the study. "This was a pretty intense predatory environment, and being able to sense the properties of the water around them would have been very important."

Convergent Evolution

The study also revealed striking parallels between these fish odontodes and sensory structures called sensilla found in the exoskeletons of arthropods like crabs and shrimp. This represents a remarkable case of convergent evolution, where vertebrates and invertebrates independently developed similar sensory mechanisms to navigate their environments.