Compounds that bind to the mineral phase of the tooth — or that are incorporated within the crystalline structure — are protected from the degradation that would rapidly destroy them in a free, unprotected state.

The mineral matrix acts as a sealed environment that limits the access of water, oxygen, and microorganisms that would otherwise break down the organic compounds.

This is why dental calculus — the mineralized plaque that builds up on tooth surfaces — has become such an important source of ancient biomolecular evidence.

Dental calculus preserves ancient proteins, ancient plant residues, ancient DNA from oral bacteria, and other organic materials across archaeological timescales.

The Sulawesi study’s detection of arecoline is in the same research tradition, applying the knowledge that teeth preserve organic chemical traces to a question about psychoactive plant use.