A veritable confusion: use and abuse of isotope analysis in archaeology

Abstract

The expansion of isotope analyses has transformed the study of past migration and mobility, sometimes providing unexpected and intriguing results. This has, in turn, led to media attention (and concomitant misrepresentation) and scepticism from some archaeologists. Such scepticism is healthy and not always without foundation. Isotope analysis is yet to reach full maturity and challenging issues remain, concerning diagenesis, biosphere mapping resolution and knowledge of the drivers of variation. Bold and over-simplistic interpretations have been presented, especially when relying on single isotope proxies, and researchers have at times been accused of following specific agendas. It is therefore vital to integrate archaeological and environmental evidence to support interpretation. Most importantly, the use of multiple isotope proxies is key: isotope analysis is an exclusive approach and therefore single analyses provide only limited resolution. The growth in isotope research has led to a growth in rebuttals and counter-narratives. Such rebuttals warrant the same critical appraisal that is applied to original research, both of evidence for their assertions and the potential for underlying agendas. This paper takes a case study-based approach focusing on pig movements to Neolithic henge complexes to explore the dangers encountered in secondary use of isotope data.

Intestinal parasites in the Neolithic population who built Stonehenge (Durrington Walls, 2500 BCE)

“…These findings emphasize the importance of coprolites in providing evidence for consumption of items that are not visible through other lines of evidence (Blong et al ., 2020 ; Shillito et al ., 2020 a ). Earlier archaeological research on animal bone and pottery residues undertaken at Durrington Walls indicates that feasts were held at the site involving large numbers of people and animals who travelled to the area, likely part of seasonal gatherings and ceremonies associated with Stonehenge and its surrounding monuments (Craig et al ., 2015 ; Evans et al ., 2019 ; Madgwick et al ., 2019 , 2021 ), and show that principally pork and beef were consumed (Albarella and Serjeantson, 2002 ; Wright et al ., 2014 ). While compound specific isotope analysis of C16:0 and C18:0 fatty acids in pottery can distinguish between carcases and dairy fats, they cannot distinguish fats from organs compared to other parts of the animal carcases.…”

“…The majority of the pigs was killed at around 9 months of age, consistent with farrowing in spring and slaughter in winter (Wright et al ., 2014 ). Isotopic analysis indicates the livestock were brought to the site from many different regions of southern Britain, providing a proxy for the catchment from which the people themselves derived (Viner et al ., 2010 ; Evans et al ., 2019 ; Madgwick et al ., 2019 , 2021 ).…”

Prehistoric communities of the River Dee

“…Relict gravel surfaces lying between the poorly drained areas would have facilitated both settlement and travel over land. Elsewhere across the UK, studies of animal and human bone have been interpreted as indicating a high degree of mobility (Parker Pearson 2015;Madgwick et al 2019Madgwick et al , 2021, though the scale of the interpretations is not without controversy (Barclay & Brophy 2020).…”

Applying lead (Pb) isotopes to explore mobility in humans and animals

“…The Sr isotope values from human cremated bone are consistent with a southern British source, but bone represents a longer biological time scale and is therefore subject to biogenic averaging [ 27 ] whereas Sr isotope values suggested that Scotland could not be excluded as a source for the animals, though recent advances in mapping raise other possibilities [ 28 ]. The discovery of highly radiogenic 87 Sr/ 86 Sr values (up to 0.7172) in Neolithic animals at the Wiltshire henges has raised the issue of whether some pigs could have been brought, as livestock, from northern Britain to Wessex during the Neolithic [ 29 , 30 ], a possibility that has sparked debate [ 31 , 32 ]. This study explores the value of Pb isotopes to this debate.…”