Three teeth.

A jaw fragment.

Twenty-five thousand years.

A psychoactive alkaloid preserved in mineral-hard dental tissue.

Frog egg cells expressing human brain receptors.

A pattern of wear that had never been formally described before this paper.

These are the elements of the oldest direct physical evidence for habitual human drug use.

The Science Advances paper published on September 9, 2026, describes a discovery that will be cited in the literature of archaeology, pharmacology, and addiction science for decades.