Ancient DNA, lipid biomarkers and palaeoecological evidence reveals construction and life on early medieval lake settlements.

A G Brown,D Pirrie,K Head,M Van Hardenbroek,G F Ficetola,P Barratt,A C G Henderson,A Crone,F Mccormick,K Davies,N J Whitehouse,P G Langdon,G Cavers,H Mackay,E Murray,L Gielly,I G Alsos,T Fonville

doi:10.1038/s41598-021-91057-x

Abstract

Direct evidence of ancient human occupation is typically established through archaeological excavation. Excavations are costly and destructive, and practically impossible in some lake and wetland environments. We present here an alternative approach, providing direct evidence from lake sediments using DNA metabarcoding, steroid lipid biomarkers (bile acids) and from traditional environmental analyses. Applied to an early Medieval Celtic settlement in Ireland (a crannog) this approach provides a site chronology and direct evidence of human occupation, crops, animal farming and on-site slaughtering. This is the first independently-dated, continuous molecular archive of human activity from an archeological site, demonstrating a link between animal husbandry, food resources, island use. These sites are under threat but are impossible to preserve in-situ so this approach can be used, with or without excavation, to produce a robust and full site chronology and provide direct evidence of occupation, the use of plants and animals, and activities such as butchery.

Highlights

Direct evidence of ancient human occupation is typically established through archaeological excavation
We reveal complex links between animal husbandry, food resources, crannog use and early anthropogenic impacts on lake ecosystems
The sedaDNA from the northern crannog and the pollen from both crannogs show that the crannogs are constructed in a partially deforested landscape but is associated with a further reduction in trees in the ninth century CE with an increase principally in grassland and in heathland

Summary

Introduction

Direct evidence of ancient human occupation is typically established through archaeological excavation. Applied to an early Medieval Celtic settlement in Ireland (a crannog) this approach provides a site chronology and direct evidence of human occupation, crops, animal farming and on-site slaughtering This is the first independently-dated, continuous molecular archive of human activity from an archeological site, demonstrating a link between animal husbandry, food resources, island use. Many sites are under threat due to the slow natural decay of associated timbers, subsidence, and erosion as a result of forest clearance on sites, changes in lake level and recreational a ctivities6—as has been demonstrated by underwater s urveys[7] There is both an archaeological and heritage need to understand more about the construction, use and abandonment of these remarkable sites before they are lost due to both natural and human-induced erosion, especially since preservation in situ is practically impossible. Traditional archaeological approaches have emphasized a wide variety of sociocultural factors including the needs of the elite (as palaces), as safe-places for people and valuable property (as protective stores) as well as cultural and ritual associations with water, myth/legends, religion and the display of wealth and power, which is certainly attested for some of the later examples[12,13]

Methods

Results

Conclusion