Unlimited fuel wood during the middle Mesolithic (9650–8300 cal. yr BP) in northern Sweden: Fuel typology and pine-dominated vegetation inferred from charcoal identification and tree-ring morphology

Abstract

A fuel wood analysis based on the ‘Principle of Least Effort’ helps to decipher the ecological limitations imposed on prehistoric hunter-gatherers. This study is based on botanical identification of wood charcoal from ‘Swedish middle Mesolithic’ archaeological sites dating from between ca. 9650 and 8300 cal. yr BP in northern Sweden, a period when the land was freshly released from ice cover. Charcoal fragments were analysed based on their anatomical and morphological features and anomalies. Tree-ring thickness gives an indication of the growing conditions experienced by woody plants, the tree-ring curvature provides an indication of the diameter of the pieces of wood used for fuel and the percentage of fragments with spiral thickening indicates the importance of compression or tension wood, which is related to branches or trunks stressed by snow burden or wind. Among the main woody species, the assemblages are dominated by Pinus sylvestris with some Salicaceae trees ( Populus, Salix). Large wood pieces including branches were used as fuel. Several taxa were rarely recorded ( Betula, Sorbus, Ericaceae) or not observed ( Juniperus, Hippophae, Alnus) although their presences were expected based on other local palaeobotanical records. Because (1) charcoal of Pinus sylvestris abounds despite not being a good fuel wood and (2) certain consumable or combustible taxa are scarce ( Betula) or are only present at certain sites (Salicaceae), it appears that Mesolithic hunters were not selective when choosing wood for fuel, although wood was not a limiting factor for the first settlers in northern Sweden. Pine tree-ring width range is within the modern range for the same species, indicating growing conditions similar to those experienced today. The results suggest the occurrence of woodland, probably in the lowlands. During the early-Holocene, trees rapidly covered the land after the ice-sheet melted, facilitating the life of Mesolithic hunters following reindeer herds.