Summary of Scientific Dating Methods in Archaeology

## Introduction Scientific dating methods are essential for building chronologies in African archaeology. The continent preserves evidence spanning the emergence of our species to recent historical societies. This guide focuses on methods and issues *other than* radiocarbon, luminescence, U-series, tephrochronology, archaeomagnetism, and rehydroxylation, which are covered elsewhere. It emphasizes practical considerations, sampling and laboratory infrastructure, combined dating strategies, and frontiers in methodological development. ## Why alternative and complementary dating approaches matter - African sites vary in preservation, depositional complexity, and available materials. - Where commonly used methods are unsuitable, archaeologists rely on other techniques, multiple independent lines of evidence, or improvements in sampling and pretreatment. - Integrating direct and indirect dating increases confidence in chronologies and helps resolve problematic calibration intervals or plateau effects. > Definition: Complementary dating — The practice of using two or more independent dating approaches or proxies to cross-check and refine age estimates for an archaeological context. ## Key practical considerations for dating projects ### 1. Context and sampling strategy - Always record the precise stratigraphic context and association of samples (feature, hearth, burial, midden). Context determines whether a sample provides a direct age for a human activity or a maximum/minimum constraint. - Prefer short-lived, single-event materials when possible (e.g., seeds, short-lived plant tissues, single amino acids) to avoid inbuilt age problems. - Use sterile tools and clean sampling bags to reduce contamination risk. > Definition: Inbuilt age — The age difference between the growth time of a dated material and the event of interest (e.g., old wood used in a later structure). ### 2. Pretreatment and contamination control - Chemical and physical pretreatments aim to remove younger or older contaminants (humic acids, rootlets, conservation adhesives). - Compound-specific approaches (targeting a single amino acid or lipid molecule) minimize contamination from mixed sources. ### 3. Laboratory selection and collaboration - Choose labs with relevant expertise and QA/QC records. For emerging or complex techniques, close collaboration with specialists improves sampling protocols and interpretation. - Consider cost, turnaround time, and availability of local facilities to reduce shipment delays and sample degradation. ## Methods and approaches (excluding those covered elsewhere) Note: Below are methods and approaches not extensively covered in the excluded list; each can complement the main dating techniques. ### A. Single-compound and compound-specific radiocarbon approaches (overview) - These target isolated molecules (for example, individual amino acids like hydroxyproline or lipids absorbed in ceramics) for dating, reducing the risks of mixed-age signals. - Application: When bone collagen is poorly preserved or bulk organic samples are contaminated. > Definition: Compound-specific dating — Dating a single molecular compound isolated from a sample to obtain a more accurate age for the associated activity. Practical example: Dating hydroxyproline extracted from bone collagen to obtain a direct age for a burial when bulk collagen contains contaminants. ### B. Electron spin resonance (ESR) combined protocols (overview) - ESR measures trapped electronic charges in mineral lattices (e.g., tooth enamel) and, when combined with other techniques (such as uranium uptake models), provides age estimates for fossil remains. - Application: Dating teeth or carbonate materials where other methods are hard to apply. > Definition: Electron spin resonance (ESR) — A technique that measures unpaired electrons trapped in crystal defects; the signal accumulates over time and can be related to dose and age. Practical example: ESR applied to hominin tooth en