Naia’s bones were not the remains of an aquatic organism, so the most direct form of the reservoir effect did not apply.

But her bones had been sitting in cave water for twelve thousand years, and cave water with a complex geological history can affect the carbon signature of the material in it over long periods.

The researchers working on the Hoyo Negro dating were aware of this potential issue and took steps to address it by dating multiple samples from different materials and by using methods that could detect inconsistencies consistent with contamination or reservoir effects.

The dates obtained from multiple samples were consistent enough that the researchers were confident in placing Naia’s death in the range of approximately 12,000 to 13,000 years before the present.