Pyrotechnologies of Middle and Later Stone Age foragers in central Africa: a micro-contextual approach

The use of fire defines us, as no other species uses fire the way we do and has such control over it. Understanding how fire was adopted into our toolkit, becoming a technology, is key to understanding who we are. Archaeological sites in the Kasitu Valley of Northern Malawi contain abundant remains of prehistoric fires, made by hunter-gatherers of the Middle and Later Stone Age. The evidence shows that hunter-gatherers did not only make fires for domestic use, e.g. for warmth and cooking, but also used the rockshelters to cremate and bury their dead, at times accompanied by big fires which are preserved as thick layers of ash.
The project “MicroAsh” targeted the “invisible” microscopic record of fire-derived sediments from three rockshelter sites to understand the evolution of pyrotechnology. Micromorphology, the study of intact sediment blocks in thin section, and microFTIR analysis on thin sections were used to study site formation processes and characterize fire features.
The overall aim of MicroAsh is to identify how prehistoric hunter-gatherers used fire for subsistence and ritual/social events in Central Africa by tracing changes in pyrotechnology and site-use across the MSA-LSA transition.

The project´s specific objectives involved:
(1) Establishing natural site formation processes and characterize fire features
(2) Investigate the (recursive) relationship between the use of fire and environmental changes
(3) Explore spatial and chronological changes in pyrotechnology
(4) Reconstruct site-use intensity

The project was structured in three main tasks: (1) fieldwork, (2) lab work, (3) analyses of reference and archaeological samples, and (4) integration of the results with environmental data.
(1) Fieldwork involved the study and documentation of archaeological sites in Malawi in July/August 2022. I sampled the sites of Mazinga-1 and Sayile (a new site) while they were being excavated. Hora-1 was re-opened for sample collection in parallel with ancient sedimentary DNA, and a small pit was excavated and sampled at Fingira, another rockshelter located on the Nyika Plateau.
To identify different components found in the archaeological deposits, samples were collected from potential sediment sources outside the rockshelters, such as soils and termite mounds, or on the rock walls, including mud wasp and swallow nests.
I also collected branches of four trees that are known by locals as most suitable for making fire, and for keeping a fire going.

(2) Labwork. To assess what plant-fuels people used for burning and what temperatures the fires reached, burning experiments were conducted in the laboratory. Samples of four non-woody plants from the Kasitu valley were already available from previous field seasons and the experiments started with these plants. After fieldwork in July/August 2022, further controlled heating experiments were conducted with woody species. As during the previous experiments, plants were heated in a muffle furnace (Nabertherm 30-3000) at 400, 500, 600, 800 and 1000 °C for 120 minutes. The ashes of the burnt specimens were made into thin sections, forming a durable reference collection.

(3) Analyses of reference and archaeological samples. All thin sections from the archaeological deposits, reference materials, and experiments, were scanned at high resolution with a flatbed scanner. Micromorphological descriptions followed guidelines by Stoops 2003 and Stoops et al. 2010.

(4) Integration of the results with environmental data (still in progress) involved integrating high-resolution geoarchaeological results with environmental data and data from the excavations.

The project was structured in three main tasks: (1) fieldwork, (2) lab work, (3) analyses of reference and archaeological samples, and (4) integration of the results with environmental data.
(1) Fieldwork involved the study and documentation of archaeological sites in Malawi in July/August 2022. I sampled the sites of Mazinga-1 and Sayile (a new site) while they were being excavated. Hora-1 was re-opened for sample collection in parallel with ancient sedimentary DNA, and a small pit was excavated and sampled at Fingira, another rockshelter located on the Nyika Plateau.
To identify different components found in the archaeological deposits, samples were collected from potential sediment sources outside the rockshelters, such as soils and termite mounds, or on the rock walls, including mud wasp and swallow nests.
I also collected branches of four trees that are known by locals as most suitable for making fire, and for keeping a fire going.

(2) Labwork. To assess what plant-fuels people used for burning and what temperatures the fires reached, burning experiments were conducted in the laboratory. Samples of four non-woody plants from the Kasitu valley were already available from previous field seasons and the experiments started with these plants. After fieldwork in July/August 2022, further controlled heating experiments were conducted with woody species. As during the previous experiments, plants were heated in a muffle furnace (Nabertherm 30-3000) at 400, 500, 600, 800 and 1000 °C for 120 minutes. The ashes of the burnt specimens were made into thin sections, forming a durable reference collection.

(3) Analyses of reference and archaeological samples. All thin sections from the archaeological deposits, reference materials, and experiments, were scanned at high resolution with a flatbed scanner. Micromorphological descriptions followed guidelines by Stoops 2003 and Stoops et al. 2010.

(4) Integration of the results with environmental data (still in progress) involved integrating high-resolution geoarchaeological results with environmental data and data from the excavations.

So far, MicroAsh has produced the following publications.

Schilt, F., Aldeias, V., Wright, D.K. Nkhata, T., Bertacchi, A., Cerezo-Román, J., Kaliba, P., Thompson, J.C. Pyrotechnologies of Middle and Later Stone Age foragers in Malawi – a micro-contextual approach with controlled heating experiments. Poster to be presented at the 21st congress of the International Union for Quaternary and Archaeological Sediments, INQUAROMA 2023.

Schilt, F.C. Aldeias, V., Thompson, J., Wright, D., Kaliba, P.M. A micro-contextual approach to pyrotechnologies of Middle and Later Stone Age foragers in central Africa. Presenting the new MicroAsh project. Poster presented at the conference of Developing International Geoarchaeology (DIG), May 2021.

I have created a freely available online selection of plant ashes in thin section for a wide audience “Atlas of Local Plants Species from the Kasitu Valley and their Ashes “.
https://fcschilt.wixsite.com/geoarch/projects-8

Further publications are pending.

Periodic Reporting for period 1 - MicroAsh (Pyrotechnologies of Middle and Later Stone Age foragers in central Africa: a micro-contextual approach)

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