Researchers analyzed ancient teeth dating back 4,000 years from an Irish limestone cave, uncovering changes in oral microbiomes since the Bronze Age. Genetic analysis showed a rare presence of Streptococcus mutans, a key decay-causing bacterium, likely due to its acid-producing nature hindering fossilization. The shift to cereal agriculture initially led to an increase in cavities, but a significant surge occurred with the introduction of sugary foods in recent centuries. This study highlights the impact of dietary changes on dental health throughout human history.