A 14C chronology for the Middle to Upper Palaeolithic transition at Bacho Kiro Cave, Bulgaria

Abstract

The stratigraphy at Bacho Kiro Cave, Bulgaria, spans the Middle to Upper Palaeolithic transition, including an Initial Upper Palaeolithic (IUP) assemblage argued to represent the earliest arrival of Upper Palaeolithic Homo sapiens in Europe. We applied the latest techniques in 14C dating to an extensive dataset of newly excavated animal and human bones to produce a robust, high-precision radiocarbon chronology for the site. At the base of the stratigraphy, the Middle Palaeolithic (MP) occupation dates to >51,000 yr bp. A chronological gap of over 3,000 years separates the MP occupation from the occupation of the cave by H. sapiens, which extends to 34,000 cal bp. The extensive IUP assemblage, now associated with directly dated H. sapiens fossils at this site, securely dates to 45,820–43,650 cal bp (95.4% probability), probably beginning from 46,940 cal bp (95.4% probability). The results provide chronological context for the early occupation of Europe by Upper Palaeolithic H. sapiens.

Access options

Rent or Buy article

Get time limited or full article access on ReadCube.

from$8.99

All prices are NET prices.

Fig. 1: Bacho Kiro Cave.
Fig. 2: A selection of bone specimens from Bacho Kiro Cave with anthropogenic surface modifications that were radiocarbon dated in this study.
Fig. 3: Bayesian chronological models for Bacho Kiro Cave.

Data availability

All data are available in the manuscript and supplementary materials.

Code availability

OxCal script is included in the supplementary information.

References

  1. 1.

    Garrod, D., Howe, B. & Gaul, J. Excavations in the cave of Bacho Kiro, north-east Bulgaria. Bull. Am. Sch. Prehist. Res. 15, 46–76 (1939).

    Google Scholar 

  2. 2.

    Kozłowski, J. K. Excavation in the Bacho Kiro Cave (Bulgaria): Final Report (Państwowe Wydawnictwo Naukowe, 1982).

  3. 3.

    Tsanova, T. Les Débuts du Paléolithique Supérieur dans l’Est des Balkans. Réflexion à Partir de l’Étude Taphonomique et Techno-Économique des En-sembles Lithiques de Bacho Kiro (Couche 11), Temnata (Couches VI et 4) et Kozarnika (Niveau VII) Vol. 1752 (BAR International Series, 2008).

  4. 4.

    Hublin, J. J. et al. Initial Upper Palaeolithic Homo sapiens remains from Bacho Kiro Cave (Bulgaria). Nature https://doi.org/10.1038/s41586-020-2259-z (2020).

    CAS  Article  Google Scholar 

  5. 5.

    Kuhn, S. L. & Zwyns, N. Rethinking the initial upper Paleolithic. Quat. Int. 347, 29–38 (2014).

    Article  Google Scholar 

  6. 6.

    Hublin, J. J. The modern human colonization of western Eurasia: when and where? Quat. Sci. Rev. 118, 194–210 (2015).

    Article  Google Scholar 

  7. 7.

    Sirakov, N. et al. Reopened Bacho Kiro—new data on Middle/Upper Palaeolithic transition and Early-Middle stages of Upper Palaeolithic (Bulgarian Academy of Sciences, 2017).

  8. 8.

    Hedges, R. E. M., Housley, R. A., Bronk Ramsey, C. & van Klinken, G. J. Radiocarbon dates from the Oxford AMS system: Archaeometry datelist 18. Archaeometry 36, 337–374 (1994).

    Article  Google Scholar 

  9. 9.

    Bird, M. et al. Radiocarbon dating of ‘old’ charcoal using a wet oxidation, stepped-combustion procedure. Radiocarbon 41, 127–140 (1999).

    CAS  Article  Google Scholar 

  10. 10.

    Wood, R. E. et al. Testing the ABOx-SC method: dating known-age charcoals associated with the Campanian Ignimbrite. Quat. Geochronol. 9, 16–26 (2012).

    Article  Google Scholar 

  11. 11.

    Brown, T. A., Nelson, D. E., Vogel, J. S. & Southon, J. R. Improved collagen extraction by modified Longin method. Radiocarbon 30, 171–177 (1988).

    CAS  Article  Google Scholar 

  12. 12.

    Bronk Ramsey, C., Higham, T., Bowles, A. & Hedges, R. Improvements to the pretreatment of bone at Oxford. Radiocarbon 46, 155–164 (2004).

    Article  Google Scholar 

  13. 13.

    Talamo, S. & Richards, M. A comparison of bone pretreatment methods for AMS dating of samples >30,000 bp. Radiocarbon 53, 443–449 (2011).

    CAS  Article  Google Scholar 

  14. 14.

    Higham, T. European Middle and Upper Palaeolithic radiocarbon dates are often older than they look: problems with previous dates and some remedies. Antiquity 85, 235–249 (2011).

    Article  Google Scholar 

  15. 15.

    Buckley, M., Collins, M., Thomas-Oates, J. & Wilson, J. C. Species identification by analysis of bone collagen using matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry. Rapid Commun. Mass Spectrom. 23, 3843–3854 (2009).

    CAS  Article  Google Scholar 

  16. 16.

    van Klinken, G. J. Bone collagen quality indicators for palaeodietary and radiocarbon measurements. J. Archaeol. Sci. 26, 687–695 (1999).

    Article  Google Scholar 

  17. 17.

    Wilson, J., van Doorn, N. L. & Collins, M. J. Assessing the extent of bone degradation using glutamine deamidation in collagen. Anal. Chem. 84, 9041–9048 (2012).

    CAS  Article  Google Scholar 

  18. 18.

    Bronk Ramsey, C. Bayesian analysis of radiocarbon dates. Radiocarbon 51, 337–360 (2009).

    Article  Google Scholar 

  19. 19.

    Reimer, P. J. et al. IntCal13 and Marine13 radiocarbon age calibration curves 0–50,000 years cal bp. Radiocarbon 55, 1869–1887 (2013).

    CAS  Article  Google Scholar 

  20. 20.

    Bronk Ramsey, C. Dealing with outliers and offsets in radiocarbon dating. Radiocarbon 51, 1023–1045 (2009).

    Article  Google Scholar 

  21. 21.

    Svensson, A. et al. A 60 000 year Greenland stratigraphic ice core chronology. Clim. Past 4, 47–57 (2008).

    Article  Google Scholar 

  22. 22.

    Cheng, H. et al. Atmospheric 14C/12C changes during the last glacial period from Hulu Cave. Science 362, 1293–1297 (2018).

    CAS  Article  Google Scholar 

  23. 23.

    Staubwasser, M. et al. Impact of climate change on the transition of Neanderthals to modern humans in Europe. Proc. Natl Acad. Sci. USA 115, 9116–9121 (2018).

    CAS  Article  Google Scholar 

  24. 24.

    Nowaczyk, N. R., Arz, H. W., Frank, U., Kind, J. & Plessen, B. Dynamics of the Laschamp geomagnetic excursion from Black Sea sediments. Earth Planet. Sci. Lett. 351-352, 54–69 (2012).

    CAS  Article  Google Scholar 

  25. 25.

    Wegwerth, A. et al. Black Sea temperature response to glacial millennial-scale climate variability. Geophys. Res. Lett. 42, 8147–8154 (2015).

    Article  Google Scholar 

  26. 26.

    Müller, U. C. et al. The role of climate in the spread of modern humans into Europe. Quat. Sci. Rev. 30, 273–279 (2011).

    Article  Google Scholar 

  27. 27.

    Giaccio, B., Hajdas, I., Isaia, R., Deino, A. & Nomade, S. High-precision 14C and 40Ar/39Ar dating of the Campanian Ignimbrite (Y-5) reconciles the time-scales of climatic-cultural processes at 40 ka. Sci. Rep. 7, 45940 (2017).

    CAS  Article  Google Scholar 

  28. 28.

    Buizert, C. et al. Abrupt ice-age shifts in southern westerly winds and Antarctic climate forced from the north. Nature 563, 681–685 (2018).

    CAS  Article  Google Scholar 

  29. 29.

    Fu, Q. et al. The genetic history of Ice Age Europe. Nature 534, 200–205 (2016).

    CAS  Article  Google Scholar 

  30. 30.

    Fewlass, H. et al. Size matters: radiocarbon dates of <200 µg ancient collagen samples with AixMICADAS and its gas ion source. Radiocarbon 60, 425–439 (2017).

    Article  Google Scholar 

  31. 31.

    Fewlass, H. et al. Pretreatment and gaseous radiocarbon dating of 40–100 mg archaeological bone. Sci. Rep. 9, 5342 (2019).

    CAS  Article  Google Scholar 

  32. 32.

    Talamo, S. et al. RESOLUTION: Radiocarbon, tree rings, and solar variability provide the accurate time scale for human evolution. In Proc. of the European Society for the Study of Human Evolution Vol. 6, 194 (ESHE, 2017); https://go.nature.com/2PnlI1h

  33. 33.

    Reimer, P. J. et al. A preview of the IntCal19 radiocarbon calibration curves. In Book of Abstracts, 23rd International Radiocarbon Conference 42 (2018); https://go.nature.com/3801Qb5

  34. 34.

    DeNiro, M. J. & Weiner, S. Chemical, enzymatic and spectroscopic characterization of “collagen” and other organic fractions from prehistoric bones. Geochim. Cosmochim. Acta 52, 2197–2206 (1988).

    CAS  Article  Google Scholar 

  35. 35.

    Yizhaq, M. et al. Quality controlled radiocarbon dating of bones and charcoal from the early pre-pottery Neolithic B (PPNB) of Motza (Israel). Radiocarbon 47, 193–206 (2005).

    CAS  Article  Google Scholar 

  36. 36.

    D’Elia, M. et al. Evaluation of possible contamination sources in the 14C analysis of bone samples by FTIR spectroscopy. Radiocarbon 49, 201–210 (2007).

    Article  Google Scholar 

  37. 37.

    Wacker, L., Němec, M. & Bourquin, J. A revolutionary graphitisation system: fully automated, compact and simple. Nucl. Instrum. Methods Phys. Res. B 268, 931–934 (2010).

    CAS  Article  Google Scholar 

  38. 38.

    Wacker, L. et al. MICADAS: routine and high-precision radiocarbon dating. Radiocarbon 52, 252–262 (2010).

    CAS  Article  Google Scholar 

  39. 39.

    Bard, E. et al. AixMICADAS, the accelerator mass spectrometer dedicated to 14C recently installed in Aix-en-Provence, France. Nucl. Instrum. Methods Phys. Res. B 361, 80–86 (2015).

    CAS  Article  Google Scholar 

  40. 40.

    Salehpour, M., Håkansson, K., Possnert, G., Wacker, L. & Synal, H.-A. Performance report for the low energy compact radiocarbon accelerator mass spectrometer at Uppsala University. Nucl. Instrum. Methods Phys. Res. B 371, 360–364 (2016).

    CAS  Article  Google Scholar 

  41. 41.

    Wacker, L., Christl, M. & Synal, H.-A. Bats: a new tool for AMS data reduction. Nucl. Instrum. Methods Phys. Res. B 268, 976–979 (2010).

    CAS  Article  Google Scholar 

  42. 42.

    Kromer, B., Lindauer, S., Synal, H.-A. & Wacker, L. MAMS—A new AMS facility at the Curt-Engelhorn-Centre for Achaeometry, Mannheim, Germany. Nucl. Instrum. Methods Phys. Res. B 294, 11–13 (2013).

    CAS  Article  Google Scholar 

  43. 43.

    Ward, G. K. & Wilson, S. R. Procedures for comparing and combining radiocarbon age determinations: a critique. Archaeometry 20, 19–31 (1978).

    CAS  Article  Google Scholar 

  44. 44.

    Welker, F. et al. Palaeoproteomic evidence identifies archaic hominins associated with the Châtelperronian at the Grotte du Renne. Proc. Natl Acad. Sci. USA 113, 11162 (2016).

    CAS  Article  Google Scholar 

  45. 45.

    Evin, J., Marien, G. & Pachiaudi, C. Lyon natural radiocarbon measurements VII. Radiocarbon 20, 19–57 (1978).

    Article  Google Scholar 

Download references

Acknowledgements

The re-excavation of Bacho Kiro Cave is a joint project between the National Institute of Archaeology and Museum, Bulgarian Academy of Sciences, Sofia and the Department of Human Evolution at the Max Planck Institute for Evolutionary Anthropology, Leipzig. This work was funded by the Max Planck Society. Graphitization and AMS dating in Switzerland were funded by ETH Zürich. The AixMICADAS and its operation are funded by the Collège de France and the EQUIPEX ASTER-CEREGE (Principle Investigator: E.B.). S.T. is funded by the European Research Council under the European Union’s Horizon 2020 Research and Innovation Programme (grant agreement No. 803147-951 RESOLUTION, awarded to S.T.). We acknowledge The National Museum of Natural History (Sofia), the Archaeology Department at New Bulgarian University (Sofia), the Regional Historical Museum in Gabrovo, the History Museum in Dryanovo and the guest house Platex in Dryanovo for their assistance in this project. We acknowledge the vital contribution of all the excavators who have worked at Bacho Kiro Cave since 2015.

Author information

Affiliations

Authors

Contributions

The study was devised by J.-J.H., S.T., S.P.M., T. Tsanova, N.S. and H.F. Archaeological excavation was undertaken by T. Tsanova, N.S., Z.R., V.A. and S.P.M., who all contributed contextual information. The 2015–2017 excavation laboratory and collection was organized by V.S.-M. Lithic analysis was performed by T. Tsanova, N.S., S.S. and S.P.M. Zooarchaeological analysis was performed by G.M.S. and R.S. N.L.M. classified the bone tools in the sample set. Stratigraphic and micromorphological analysis was carried out by V.A. ZooMS was carried out by F.W., L.P. and V.S.-M. Sample pretreatment and EA-IRMS analyses were carried out by H.F. FTIR analyses were carried out by H.F. and R.M. Graphitization and AMS dating at ETH Zürich was carried out by L.W., B.K. and H.F. Dating with the AixMICADAS was carried out by E.B., Y.F. and T. Tuna. Bayesian modelling was carried out by H.F. and S.T. H.F. wrote the paper with input from all authors.

Corresponding author

Correspondence to Helen Fewlass.

Ethics declarations

Competing interests

The authors declare no competing interests.

Additional information

Publisher’s note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Extended data

Extended Data Fig. 1 Photograph of Bacho Kiro Cave excavations in 2019.

View of the Niche 1 (left) and Main Sector (right), looking toward the south in the cave. The concrete floor in the centre covers the 1970s excavation area.

Extended Data Fig. 2 Bacho Kiro Cave, excavation 2015-2018.

a, Plan view of the entry hall and the excavated area, with the grid system of the recent excavations (black letters) and those of the 1971-75 excavations (grey letters). Red lines indicate the locations of the profile columns from Niche 1 (b) and Main Sector (c). b, Stratigraphic section-log in the Niche 1 in 2018. Layer attributions in the Niche 1 have an ‘N1-‘ prefix. c, Initial stratigraphic section-log in the Main Sector in 2015. Numbers in parentheses show the layer attributions from the 1970s excavations. Legend for the stratigraphic units shown on the left.

Extended Data Fig. 3 Collagen yields (%) of pretreated bones.

a, Main Sector and b, Niche 1, separated by layer and layer contact zones (I/J, N1-J/K, N1-I/J, N1-H/I). The dashed line shows the minimum level of collagen preservation generally considered suitable for 14C dating.

Extended Data Fig. 4 Comparison of radiocarbon dates of Homo sapiens bones F6-597 and BK-1653.

a, F6-597 comes from Layer B of the new excavations and b, BK-1653 comes from the 1970s collection (Layer 6a/7) that is stored in the National Museum of Natural History in Sofia. The purple range shows the weighted mean age and error of all the dates measured from graphite targets and directly from CO2 gas (shown in Supplementary Table 6), calculated using the R_Combine function in OxCal 4.345.

Supplementary information

Supplementary Information

Supplementary Text 1–6, Figs. 1–6 and Tables 1 and 6.

Reporting Summary

Supplementary Tables

Supplementary Tables 2–5 with pretreatment information, AMS data and modelling output.

Supplementary Data

OxCal code for Bayesian models (Main Sector and Niche 1) presented in the paper.

Rights and permissions

Reprints and Permissions

About this article

Verify currency and authenticity via CrossMark

Cite this article

Fewlass, H., Talamo, S., Wacker, L. et al. A 14C chronology for the Middle to Upper Palaeolithic transition at Bacho Kiro Cave, Bulgaria. Nat Ecol Evol 4, 794–801 (2020). https://doi.org/10.1038/s41559-020-1136-3

Download citation

Further reading

Search

Nature Briefing

Sign up for the Nature Briefing newsletter — what matters in science, free to your inbox daily.

Get the most important science stories of the day, free in your inbox. Sign up for Nature Briefing