The original teeth are sensors, not chewers

Scientists have found that vertebrates initially evolved into sensory organs, not just dietary tools, according to new research published in nature.

The study uses cutting-edge synchronous accelerator scanning technology to reveal that the earliest tooth-like structures in ancient fish were designed to detect environmental changes, just like modern touch sensors. This discovery overturned long-standing scientific controversy and delayed the origins of real vertebrate dental tissue until the mid-Odovic period.

Research teams at the University of Chicago, Harvard and other institutions have discovered their findings while investigating the controversial Cambrian fossils that were previously considered the earliest vertebrate teeth. Instead, they found that these ancient structures belonged to the dependence of arthropods – modern crabs and insects.

Identity error situation

Paleontologists have debated for decades about the fossils called Anatolepis Heintzi, which some researchers claim is the earliest vertebrate residue that contains dentin, which is most of the tissue that forms modern teeth. The 500 million-year-old fragment appears to have a characteristic tubular structure found in vertebrate dental tissue.

The team used a powerful synchronizer X-ray tomography from Argonne National Laboratory to find that these so-called dental tissues are actually sensory structures from ancient arthropods called Aglaspidids. Tubules previously identified as dentin have been shown to be similar to those in modern crabs and other arthropods.

Misidentification occurs because both vertebrate teeth and arthropod sensory organs evolved very similar internal structures. Both have branched tubules radiating from the central cavity, creating what scientists call “convergence evolution”, when irrelevant organisms would produce similar characteristics to solve comparable problems.

Really discovered the real vertebrate teeth

With the elimination of Cambrian competitors, researchers turned from 470 million years ago toward Mesoorodian fossils to find true vertebrate dental tissue. They examined the old fish species found in the Wyoming Harding Sandstone and the tooth-like structure of Astraspis, called teeth.

These early vertebrate teeth showed clear signs of sensory function. Eriptychius Odondodes lacks the protective enamel coating found in the teeth later, exposing dental tubules to the environment, a feature that can cause extreme sensitivity in modern animals. These structures also maintain an open pulp cavity connected to the nervous system.

Modern evidence supports ancient functions

To test whether today’s sensory function persists, researchers used advanced immunofluorescence techniques to examine the external dental sample scales of modern fish. They studied teenage cat sakers, sledge skates and catfish, and found a wide range of neural networks related to these structures.

Analysis shows that modern fish retains significant neuroneurized nerves in their outer cylinder, i.e., the evolutionary predecessor of the teeth. In catfish, nerves actually penetrate the flesh cavity of the fins, while in sharks, neural networks surround the bottom of the body’s scale.

Main research results

• Cambrian fossils were previously considered the earliest vertebrate teeth actually belong to arthropods with sensory organs
• True vertebrate dental tissue is first thought
• Early vertebrate teeth showed clear adaptation to sensory function, not just feeding
• Modern fish retains a wide range of teeth-like nerves, supporting the theory of sensory evolution
• Convergent evolution produces structures very similar in vertebrates and arthropods to perceive environmental changes

Why do you feel that teeth have evolutionary significance

The sensory origin of teeth helps explain several confusing features of modern vertebrate biology. Why are teeth so sensitive to pain? Why do animals like the nasal cavity have teeth that are primarily used as sensory organs? The answer may lie in their evolutionary history as environmental sensors.

For early vertebrates wrapped in bone armor, maintaining sensory contact with the environment is crucial for survival. Teeth-like structures provide a solution – they can provide protection while collecting information about water chemistry, food quality and potential threats.

This concept of “sensory armor” goes beyond vertebrates. Modern arthropods use similar structures for environmental sensing, which suggests that this is a broad evolutionary solution to the challenge of maintaining awareness while being protected.

Technical breakthroughs make discovery

This study was only due to advances in synchronous X-ray technology, which could reveal internal structures without destroying precious fossils. The team scanned 35 different species, including extinction and survival, to build a comprehensive database of skeletal tissue.

High resolution scanning reveals invisible details by previous microscopy techniques, including the unique “in-tube” structure of arthropod sensory organs that are different from real vertebrate dentins. This level of detail allows researchers to clearly distinguish between two tissue types.

Understand the impact of life

This discovery reshapes our understanding of how complex sensory systems develop in early animals. Vertebrates did not seem to develop feeding structures, and later the sensory system that vertebrates seemed to have evolved, later suitable for food processing.

The discovery also emphasizes that convergent evolution can even deceive expert scientists. When similar environmental pressures work on different lineages, the final solution is almost indistinguishable without complex analytical tools.

As researchers continue to study the vast archives of ancient life preserved in fossils, this technological advancement is expected to reveal more surprises about how fundamental biological systems develop. Other assumptions about early life might overturn imaging technology?

Research shows that even our most basic traits, such as teeth, are more complex and interesting than previously thought.

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