Sedimentary unknowns constrain the current use of frequency analysis of radiocarbon data sets in forming regional models of demographic change

Abstract

Statistical manipulation of large radiometric data sets (big data) is increasingly applied to those grand challenges in archaeology that relate to past human‐behavioural dynamics and includes frequency analysis of radiocarbon ages (summed probability distributions [SPDs]). Australian SPD studies use the radiocarbon database “AustArch” to examine regional‐ and continental‐scale demographic change. We review Australian studies, focussing on sampling bias and taphonomic bias, finding that (i) time‐averaged radiometric data cannot simply be correlated across regions, and (ii) sedimentology imposes genuine constraints upon what can be known. Internationally, flaws in SPD use occur in all main research phases, and most importantly, at the initial phase of defining research questions, logic and general approach. Major problems stem from not planning to obtain a sound understanding of the variability of past sedimentary environments, potential occupation sites and site formation processes. Thus, cultural inferences are too often made from archaeological data without due consideration of the natural processes that may explain the data. Highlighting exemplar studies, we present practical approaches to improve SPD use for exploring changes in demography, aimed at reducing uncertainties and reconnecting archaeological, chronological, geological and sedimentary data. Most important is to increase understanding of physical processes and their control on the archaeological record.

RETRACTED: Applying geoarchaeological principles to marine archaeology: A reappraisal of the “first marine” and “in situ” lithic scatters in the Dampier Archipelago, NW Australia

“…Hence, a key stage in the evaluation of these data is a comprehensive assessment of the physical setting and processes to which components of both the onshore and submerged archaeological assemblages may have been subjected (Stewart, 1999; Ward et al, 2014, 2015). Oceanographic and sedimentary evidence is a critical part of this (Caporaso, 2017; Larcombe & Ward, 2018; Larcombe et al, 2018), just as it is vital to understand soil processes for terrestrial archaeology (e.g., Karkanas & Goldberg, 2019; Walkington, 2010; Ward & Larcombe, 2003, 2021). This assessment must include the impacts of tropical cyclones and other drivers, over multiple years and simulated over multiple millennia, in concert with potential changes in coastal configuration.…”

Approximate Bayesian Computation of radiocarbon and paleoenvironmental record shows population resilience on Rapa Nui (Easter Island)

“…Samples come from across the island and derive from similar sedimentary contexts resulting from anthropogenic depositional events 75 , cf. 25 . These steps resulted in 201 dates from 47 locations.…”

“…From a methodological standpoint, the generative inference approach provided by ABC offers a solution that addresses the need to evaluate complex demographic models with sufficient statistical rigor while also taking into account the specific challenges of radiocarbon datasets. The main advantage of the ABC approach for model fitting and comparison over recently suggested approaches 33,34,45 is the flexibility offered by formulating the proposed model as a simulation, an advance that could potentially integrate more complex phenomena involved in shaping SPDs such as settlement dynamics 96 and geoarchaeological concerns such as taphonomy 97 and variable sedimentation rates 25 . While the price for this flexibility is the relatively high computational requirements, this factor is outweighed by the benefits gained from more fully characterizing analytical uncertainty, opening up opportunities for empirically testing an increasing number of computational models, and ultimately improving the accuracy of the inferential process in archeology.…”

“…Researchers have examined multiple proxies for reconstructing ancient demographic patterns [10][11][12][13][14] , but the use of radiocarbon frequency data is currently the most widely used approach in archeology [15][16][17][18][19][20] . Despite interpretative and methodological challenges [21][22][23][24][25] , the unmatched chronological resolution and the increasing availability of large collections of 14 C dates offer unique opportunities for comparative demographic research. While there have been several methodological advances overcoming many of the early limitations of this approach, two current weaknesses remain: (1) appropriate means of formal multi-model comparison and (2) methods for directly modeling demographic effects of environmental variables.…”

Statistical inference of prehistoric demography from frequency distributions of radiocarbon dates: a review and a guide for the perplexed

“…Rick's gambit hinges on the assumption that the aggregate frequency of radiocarbon dates associated with different anthropic events correlates with population density, retaining a reliable signal by evening out its underlying heterogeneity. A fairly large number of papers have discussed in detail how this assumption can be problematic (Attenbrow and Hiscock 2015, Torfing 2015, Becerra-Valdivia et al 2020, Ward and Larcombe 2021. While this is unquestionably an important issue, I will not add much more to the debate for two reasons.…”