U–Pb dating of cave sediments has provided important new time constraints on the evolution of cave-dwelling organisms (including early humans) and of Earth's climate during the past 5 Myr. This paper shows that the most common type of U–Pb dating, which uses ²³⁸U and ²⁰⁶Pb, can be inaccurate beyond ca. 2 Myr ago. It proposes an alternative type of U–Pb dating, using ²³⁵U and ²⁰⁷Pb, as a more accurate alternative.