A critique of vole clocks

• This paper examines the accuracy and value of “vole clocks.”
• Recent studies using vole clocks are critiqued.
• Sampling and dating issues alone preclude clock accuracy.
• Vole clocks are unrealistic because size does not “decay” like a radioisotope.

Recent attempts to estimate the age of deposition of European fossil localities using mathematical equations derived from size change of the first lower molar in arvicolid rodent lineages as a function of time prompted an assessment of the value of this approach. The accuracy of “vole clocks” depends on accurate dating of a fossil system and establishment of a directional size change pattern through time in a given species from the dated system. Results of this review suggest that vole clocks have limited value for biochronology. In addition to several methodological and statistical problems with published studies, vole clocks in general are untenable because paleontological systems cannot resolve dating to the level of accuracy necessary to construct an accurate equation, size and shape change is never monotonic (constant velocity) in lineages, and size commonly reverses direction in lineages on all time scales.

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