Biology subjects

Dierickx, K.

Publications and source records attributed to Dierickx, K..

3 recordsLinked to original sources

bioRxiv2026

Of bone and ivory: Eastern Atlantic sources of the medieval European walrus ivory trade discovered by ancient mitochondrial and nuclear DNA

Previous molecular archaeological research has made the surprising discovery that almost all studied European walrus finds dating between the 11th and 14th centuries CE seemed to be traded from the Norse colony of Greenland. But why has almost no walrus ivory from the Barents Sea region been detected in medieval Europe, despite its closer proximity and being mentioned in historical accounts? Here, we show that the full spatial extent of medieval Atlantic walrus hunting has been underestimated in previous analyses that targeted modified walrus skulls (rostra) with which pairs of attached tusks were traded, because destructive sampling of ivory artefacts is not always practicable. By analysing workshop offcuts from medieval Sigtuna, Sweden, we directly compare the geographical sources of walrus ivory with rostra, and show that isolated tusks were traded in different ways. We first resolve the genome-wide trans-Atlantic walrus population structure, discovering significant genome-wide nuclear differentiation between western and eastern Atlantic walrus populations. By employing spatially diagnostic nuclear SNPs (n = 144,986), we then use low-coverage sequence data to classify historical walrus rostrum and tusk specimens to either western or eastern Atlantic origin, and thus overcome previous limitations when provenancing walruses based on mitochondrial DNA alone. We find that all medieval walrus rostra are assigned exclusively towards the western Atlantic. In contrast, half of the medieval ivory specimens from Sigtuna are assigned to eastern Atlantic sources including Iceland and the Barents Sea region. Moreover, the objects of eastern origin precede those from Norse Greenland in time, suggesting sequential exploitation. Our observations resolve a discrepancy between earlier molecular inference and historical evidence and imply a significantly broader extent and impact of medieval ecological globalisation in the Arctic.

evolutionary biology↗

bioRxiv2026

Walrus Population-specific Marine Reservoir Offsets (ΔR) for Calibration of Radiocarbon Dates: Implications for Arctic Chronologies and Medieval Trade

Walruses have long played a vital role in Arctic subsistence and commercial economies, yet accurate radiocarbon dating of walrus-derived archaeological materials is complicated by regional variation in marine reservoir effects. This study presents new {Delta}R values derived from 31 new and 15 legacy radiocarbon dates on known-age walrus specimens spanning multiple populations of Odobenus rosmarus rosmarus and O. r. divergens. The results reveal substantial inter-population variability, with {Delta}R values ranging from -140 (Franz Josef Land) to +295 (Pacific), underscoring the importance of population-specific calibration. A pooled {Delta}R of +17{+/-}12 was calculated for western Greenland and the Canadian Arctic--regions central to the medieval Norse ivory trade--and applied to 12 walrus rostra and ivory artefacts excavated in Trondheim, Norway. The resulting calibrated dates are from the 11th to early 14th centuries CE, confirming that seemingly anomalous post-15th-century finds are residual rather than evidence of continued trade. An alternative {Delta}R estimate of -110{+/-}35, derived solely from archaeological context dates, suggests potential time lags between harvest and deposition. These findings demonstrate the value of known-age walrus {Delta}R data for refining chronologies of Arctic exploitation and long-distance trade, while highlighting the need for provenance studies in archaeological dating and both the pertinence and limitations of mollusk-based reservoir corrections.

paleontology↗

bioRxiv2024

The Once and Future Fish: 1300 years of Atlantic herring population structure and demography revealed through ancient DNA and mixed-stock analysis

Atlantic herring populations have been the target of highly profitable coastal and pelagic fisheries in northern Europe for well over a thousand years. Their complex and intermingled population dynamics have sparked extensive debate over the impacts of historical overfishing and have complicated their sustainable management today. Recently developed tools - including diagnostic SNP panels for mixed-stock analysis - aim to improve population assignment for fisheries management, however, the biological relevance of such tools over long periods of time remains unknown. Here, we demonstrate the millennium-long applicability of diagnostic SNP panels and identify population perturbations associated with increasing exploitation pressure and climate change by analyzing whole genome data from modern and ancient herring specimens. We find that herring demographic cycles were likely within healthy ecosystem boundaries until the dramatic disruption of these cycles in the 20th century. We find only autumn-spawning herring in our archaeological remains spanning 900 years from 8 sites across Europe, supporting observations that the numerical dominance of specific spawning populations can demographically outcompete other herring types. We also obtain pre-archival aDNA evidence for the famous, cyclical "Bohuslan periods," during which mass quantities of North Sea autumn-spawning herring congregated in the Skagerrak. Finally, the long-term applicability of diagnostic SNP panels underscores their highly cost-effective application for the genetic monitoring of herring stocks. Our results highlight the utility of ancient DNA and genomic analysis to obtain historical and natural insights in herring ecology and population dynamics with relevance for sustainable fisheries management.

ecology↗