Summary of "Why Evolution Made Your Teeth Hurt"

Brief summary

Our teeth evolved from hard, sensory skin armor — dermal “teeth” (odontodes) — used by early jawless fishes for protection and environmental sensing. The internal structure that allowed those dermal plates to transmit sensory information (pulp + dentin with tubules connected to nerves) is the reason modern teeth can be extremely sensitive or painfully reactive when enamel is damaged.

Evolutionary origin and key steps

Early jawless and bony fishes developed dentin-based dermal armor with pores/tubules linking to a pulp cavity and nerves. These structures functioned both as protection and as sensory organs.
Some groups later added outer mineral layers analogous to enamel to increase surface hardness and protection; in some lineages the pulp was partially or fully filled in to reduce sensitivity.
True dental enamel in the mouth appeared later — in the Devonian in early sarcopterygians — enabling stronger biting and broader diets, including herbivory.

Scientific concepts, discoveries, and natural phenomena

Cambrian predator arms race: around 530 million years ago an explosion of predators drove defensive innovations across many lineages.
Dermal odontodes: skin “teeth” made of dentin evolved in jawless/bony fishes (roughly 500–460 mya) as external armor that also served sensory roles.
Dentin structure: porous, with tiny branching tubules that open to the surface via pores and connect inward to a soft pulp cavity tied to nerves. This arrangement transmits mechanical, thermal, chemical, and electrical cues.
Trade-off of protection vs. sensation: armored plates protected soft tissue and provided muscle attachment and mineral storage, but they maintained channels for environmental sensing.
Mineral coatings and enamel-like layers evolved in some taxa to increase surface hardness; in some lineages sensitivity was reduced by filling the pulp.
Functional consequence: enamel + dentin strengthened teeth for biting and grinding, enabling dietary diversification (e.g., herbivory). However, dentin’s tubules beneath enamel still transmit stimuli, explaining modern tooth sensitivity (cold, cavities, cracks, sugar) and sometimes pain disproportionate to damage.
Teeth as sensory relics: the painful sensitivity of modern teeth is an evolutionary carryover from sensory dermal structures in ancient fishes.

Functional roles proposed for dermal armor

Physical protection of head and vital soft tissues from predators and abrasion
Structural stiffening for swimming (muscle attachment)
Mineral storage where coastal/shallow environments limited mineral availability
Sensory interface: pores and tubules transmitted mechanical, thermal, chemical, and electrical information to nerves

Modern tooth structure

Pulp: soft inner chamber containing nerve fibers and sensory receptors.
Dentin: the layer surrounding pulp, with microscopic tubules that convey stimuli.
Enamel: the hardest outer layer that protects dentin; when enamel is damaged or lost, the underlying dentin transmits pain.

Why our teeth hurt (concise) Teeth retain dentin tubules connected to pulp/nerves — a legacy of sensory dermal teeth. If enamel is cracked, worn away, or temperature/chemicals stimulate dentin tubules, the pulp senses and produces sharp or disproportionate pain — an evolutionary side-effect of teeth that were originally sensory armor.

Timeline / examples

~530 mya: Early Cambrian predator diversification begins.
~500–460 mya: Early jawless fishes begin developing dentin-based dermal armor (examples cited in the subtitles: “Arapticius” / variations).
~450 mya: Dermal plates with porous dentin and pulp cavities present in shoreline/bottom-dwelling fishes.
~420 mya: “Andrea Lepis” (in subtitles) — fully covered in dermal teeth and also had replaceable oral teeth of dentin; scales began to gain enamel in some groups.
Late Silurian: “Sarah Lepus” (as named in subtitles) had enamel on body/head dermal plates though oral teeth still had exposed dentin.
Devonian (~<400 mya): Dental enamel appears on the teeth of early sarcopterygians, strengthening teeth and supporting new diets.