Fish had toothaches 465 million years ago

Teeth are covered with a layer of enamel on the outside and, on the inside, they have a layer known as dentin, which is responsible for carrying signals to the nerves when we bite into something hard or eat something extremely cold or too sweet. The scientific community explains that teeth originate from small bumps that developed on the hard, outer shells of ancient fish. Now, there is a new study that shows that fish from the Ordovician period, 465 million years ago, had dentin, which indicates that they could experience toothache.

Using 3D mapping of fish fossils, a team of researchers found that these humps were sensitive and presumably used to sense the environment, such as detecting cold water or pressure from nearby objects. The humps also resemble sensory organs found in crabs and shrimp, as well as in fossils of ancient invertebrates.

Yara Haridy, who led the study, explains that this is an evolutionary convergence, where different species such as fish and arthropods end up developing similar traits. “We know that vertebrates and arthropods evolved rigid parts independently and surprisingly evolved similar sensory mechanisms integrated into their rigid skeletons independently,” cites Interesting Engineering .

Both groups eventually developed ways to sense the external environment using nerve-connected structures embedded in their hard coverings, from the skin of fish to the shells of crabs. The comparison between the two groups was made by analyzing fossils and more modern specimens, from crabs and mussels to fish and sharks. One of the fish developed in the lab had tiny tooth-like scales called denticles directly connected to the nerves. “We think that the first vertebrates, the large fish with 'armor', had very similar structures,” says Haridy.

The hypothesis now under consideration suggests that teeth as we know them evolved from external sensory structures like these, that is, before animals had mouths full of teeth, it was these sensory mounds that helped them survive. Read the full study published in Nature .