Teeth Sensitivity Linked to 500-Million-Year-Old Fish, Study Reveals - Bio Points News

Paris, France (May 21, 2025): A groundbreaking study suggests that the sensitivity of human teeth to pain or cold drinks may trace back to their origins as sensory organs in ancient fish 500 million years ago. Published in Nature, the research sheds light on the evolutionary roots of teeth, revealing they likely first appeared not for chewing but as part of the external armor of early vertebrates, acting as sensory structures.

The study, led by postdoctoral researcher Yara Haridy at the University of Chicago, initially aimed to identify the oldest fossil of a backbone-bearing animal. However, Haridy’s analysis of hundreds of microscopic vertebrate fossils, sourced from U.S. museums and scanned with a CT scanner, shifted focus to dentine—the inner tooth layer that relays sensory information to nerves. This discovery challenges long-standing theories about the purpose of early teeth, known as odontodes, found on ancient fish like sharks and stingrays.

From Armor to Sensory Organs

Odontodes, hard structures on the skin of early fish, are considered the precursors to modern teeth. While some theories suggest they served as protection, aided movement, or stored minerals, Haridy’s team found evidence that odontodes were primarily sensory, transmitting environmental cues to nerves. This aligns with their presence in modern species, where microscopic teeth on shark skin act like sensory sandpaper. “Our findings suggest teeth evolved to ‘feel’ the world before they were used to chew,” Haridy told AFP.

A Deep Dive into Dentine

Haridy’s focus on dentine, which connects to nerve-rich pulp in teeth, revealed its sensory role in ancient vertebrates. By examining fossils as small as a toothpick tip, her team traced dentine’s structure back 500 million years, linking it to the nervous system of early fish. This sensory function explains why modern teeth are so sensitive, as their evolutionary design prioritized sensation over mechanical strength.

Implications for Evolution

The study redefines the timeline of vertebrate evolution, suggesting sensory odontodes were a critical adaptation in early fish, predating oral teeth. Posts on X, like @SciNewsDaily, hailed the research as a “game-changer for palaeontology,” while @PaleoPulse noted its implications for understanding shark skin and human dental sensitivity. The findings also raise questions about other vertebrate traits, with Haridy planning to explore bone development next.

As scientists unravel the 500-million-year-old mystery, the study underscores how ancient adaptations continue to shape modern biology, from the sting of a cold drink to the resilience of our teeth.