Skip to main content

Thank you for visiting You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript.

Stratigraphic placement and age of modern humans from Kibish, Ethiopia


In 1967 the Kibish Formation in southern Ethiopia yielded hominid cranial remains identified as early anatomically modern humans, assigned to Homo sapiens1,2,3,4. However, the provenance and age of the fossils have been much debated5,6. Here we confirm that the Omo I and Omo II hominid fossils are from similar stratigraphic levels in Member I of the Kibish Formation, despite the view that Omo I is more modern in appearance than Omo II1,2,3. 40Ar/39Ar ages on feldspar crystals from pumice clasts within a tuff in Member I below the hominid levels place an older limit of 198 ± 14 kyr (weighted mean age 196 ± 2 kyr) on the hominids. A younger age limit of 104 ± 7 kyr is provided by feldspars from pumice clasts in a Member III tuff. Geological evidence indicates rapid deposition of each member of the Kibish Formation. Isotopic ages on the Kibish Formation correspond to ages of Mediterranean sapropels, which reflect increased flow of the Nile River, and necessarily increased flow of the Omo River. Thus the 40Ar/39Ar age measurements, together with the sapropel correlations, indicate that the hominid fossils have an age close to the older limit. Our preferred estimate of the age of the Kibish hominids is 195 ± 5 kyr, making them the earliest well-dated anatomically modern humans yet described.

This is a preview of subscription content, access via your institution

Relevant articles

Open Access articles citing this article.

Access options

Rent or buy this article

Prices vary by article type



Prices may be subject to local taxes which are calculated during checkout

Figure 1: Map showing the distribution of the Kibish Formation (shaded) in the lower Omo Valley, southern Ethiopia, after Davidson29.
Figure 2: Composite stratigraphy of the Kibish Formation.


  1. Day, M. H. Omo human skeletal remains. Nature 222, 1135–1138 (1969)

    Article  ADS  CAS  Google Scholar 

  2. Day, M. H. & Stringer, C. B. in Congrès International de Paléontologie Humaine I, Nice Vol. 2, 814–846 (Colloque International du CNRS, 1982)

    Google Scholar 

  3. Day, M. H. & Stringer, C. B. Les restes crâniens d'Omo-Kibish et leur classification à l'intérieur du genre Homo . Anthropologie 95, 573–594 (1991)

    Google Scholar 

  4. Day, M. H., Twist, M. H. C. & Ward, S. Les vestiges post-crâniens d'Omo I (Kibish). Anthropologie 95, 595–610 (1991)

    Google Scholar 

  5. Howell, F. C. in Evolution of African Mammals (eds Maglio, V. J. & Cooke, H. B. S.) 154–248 (Harvard Univ. Press, Cambridge, Massachusetts, 1978)

    Google Scholar 

  6. Smith, F. H., Falsetti, A. B. & Donnelly, S. M. Modern human origins. Yb Phys. Anthropol. 32, 35–68 (1989)

    Article  Google Scholar 

  7. Butzer, K. W., Isaac, G. Ll., Richardson, J. L. & Washbourn-Kamau, C. Radiocarbon dating of East African lake levels. Science 175, 1069–1076 (1972)

    Article  ADS  CAS  Google Scholar 

  8. Fuchs, V. E. The geological history of the Lake Rudolf Basin, Kenya Colony. Phil. Trans. R. Soc. Lond. B 229, 219–274 (1939)

    Article  ADS  Google Scholar 

  9. Arambourg, C. Mission Scientifique de l'Omo 1932–1933. Geologie–Anthropologie–Paleontologie (Muséum National d'Histoire Naturelle, Paris, 1935–1947)

    Google Scholar 

  10. Butzer, K. W. The Lower Omo Basin: Geology, fauna and hominids of Plio-Pleistocene formations. Naturwissenschaften 58, 7–16 (1971)

    Article  ADS  CAS  Google Scholar 

  11. Butzer, K. W. in Earliest Man and Environments in the Lake Rudolf Basin (eds Coppens, Y., Howell, F. C., Isaac, G. Ll. & Leakey, R. E. F.) 12–23 (Univ. of Chicago Press, Chicago, 1976)

    Google Scholar 

  12. Butzer, K. W. & Thurber, D. L. Some late Cenozoic sedimentary formations of the Lower Omo Basin. Nature 222, 1138–1143 (1969)

    Article  ADS  Google Scholar 

  13. Butzer, K. W., Brown, F. H. & Thurber, D. L. Horizontal sediments of the lower Omo Valley: the Kibish Formation. Quaternaria 11, 15–29 (1969)

    Google Scholar 

  14. Butzer, K. W. Geological interpretation of two Pleistocene hominid sites in the Lower Omo Basin. Nature 222, 1133–1135 (1969)

    Article  ADS  Google Scholar 

  15. Owen, R. B., Barthelme, J. W., Renaut, R. W. & Vincens, A. Palaeolimnology and archaeology of Holocene deposits north-east of Lake Turkana, Kenya. Nature 298, 523–529 (1982)

    Article  ADS  Google Scholar 

  16. Fleagle, J. et al. The Omo I partial skeleton from the Kibish Formation. Am. J. Phys. Anthropol. Suppl. 36, 95 (2003)

    Google Scholar 

  17. Lourens, L. J. et al. Evaluation of the Plio-Pleistocene astronomical timescale. Paleoceanography 11, 391–413 (1996)

    Article  ADS  Google Scholar 

  18. Rossignol-Strick, M., Nesteroff, W., Olive, P. & Vergnaud-Grazzini, C. After the deluge: Mediterranean stagnation and sapropel formation. Nature 295, 105–110 (1982)

    Article  ADS  Google Scholar 

  19. Rossignol-Strick, M. & Paterne, M. A synthetic pollen record of the eastern Mediterrranean sapropels of the last 1 Ma: implications for the time-scale and formation of sapropels. Mar. Geol. 153, 221–237 (1999)

    Article  ADS  Google Scholar 

  20. Rohling, E. J. et al. African monsoon variability during the previous interglacial maximum. Earth Planet. Sci. Lett. 202, 61–75 (2002)

    Article  ADS  CAS  Google Scholar 

  21. Haile-Selassie, Y., Asfaw, B. & White, T. D. Hominid cranial remains from Upper Pleistocene deposits at Aduma, Middle Awash, Ethiopia. Am. J. Phys. Anthropol. 123, 1–10 (2004)

    Article  CAS  Google Scholar 

  22. Rightmire, G. P. in The Origins of Modern Humans: A World Survey of the Fossil Evidence (eds Smith, F. H. & Spencer, F.) 295–325 (Alan R. Liss, New York, 1984)

    Google Scholar 

  23. Howell, F. C. in Origins of Anatomically Modern Humans (eds Nitecki, M. H. & Nitecki, D. V.) 253–319 (Plenum, New York, 1994)

    Book  Google Scholar 

  24. Clark, J. D. et al. Stratigraphic, chronological and behavioural contexts of Pleistocene Homo sapiens from Middle Awash, Ethiopia. Nature 423, 747–752 (2003)

    Article  ADS  CAS  Google Scholar 

  25. McDougall, I. & Feibel, C. S. Numerical age control for the Miocene–Pliocene succession at Lothagam, a hominoid-bearing sequence in the northern Kenya Rift. J. Geol. Soc. Lond. 156, 731–745 (1999)

    Article  CAS  Google Scholar 

  26. Spell, T. L. & McDougall, I. Characterization and calibration of 40Ar/39Ar dating standards. Chem. Geol. 198, 189–211 (2003)

    Article  ADS  CAS  Google Scholar 

  27. Spell, T. L., McDougall, I. & Doulgeris, A. P. The Cerro Toledo Rhyolite, Jemez Volcanic Field, New Mexico: 40Ar/39Ar geochronology of eruptions between two caldera-forming events. Bull. Geol. Soc. Am. 108, 1549–1566 (1996)

    Article  Google Scholar 

  28. York, D. Least squares fitting of a straight line with correlated errors. Earth Planet. Sci. Lett. 5, 320–324 (1969)

    Article  ADS  CAS  Google Scholar 

  29. Davidson, A. The Omo River Project (Bulletin 2, Ethiopian Institute of Geological Surveys, Addis Ababa, 1983)

    Google Scholar 

Download references


We thank J. Mya, R. Maier and X. Zhang for technical support for the geochronology; participants in the Kibish expeditions between 1999 and 2003, including Z. Assefa, J. Shea, S. Yirga, J. Trapani and especially C. Feibel, B. Passey and C. Fuller for their geological contributions; and R. Leakey, K. Butzer and especially P. Abell for providing us with information and documents about the 1967 expedition to the Kibish area. We thank the Government of Ethiopia, the Ministry of Youth, Sports and Culture, the Authority for Research and Conservation of Cultural Heritage, and the National Museum of Ethiopia for permission to study the Kibish Formation. Support was provided by the National Science Foundation, the Leakey Foundation, the National Geographic Society and the Australian National University. Neutron irradiations were facilitated by the Australian Institute of Nuclear Science and Engineering and the Australian Nuclear Science and Technology Organization.

Author information

Authors and Affiliations


Corresponding author

Correspondence to Ian McDougall.

Ethics declarations

Competing interests

The authors declare that they have no competing financial interests.

Supplementary information

Supplementary Table 1

Electron Microprobe analysis of glass from tuffs and pumice of the Kibish Formation. (XLS 22 kb)

Supplementary Table 2

Results of laser fusion 40Ar/39Ar dating of alkali feldspar crystals from two pumice clasts (mass ~5 g) from Member I, Kibish Formation, west of Omo River at Nakaa'kire, 1 km north of Aliyo, Ethiopia (5°24.59'N, 35°54.52'E). (DOC 50 kb)

Supplementary Table 3

Results of laser fusion 40Ar/39Ar dating of alkali feldspar crystals from three pumice clasts in a tuff of Member I, Kibish Formation, west of Omo River at Nakaa'kire, near Omo II site, Ethiopia (5°24.6'N, 35°54.5'E). (DOC 87 kb)

Supplementary Table 4

Results of laser fusion 40Ar/39Ar dating of alkali feldspar crystals from two pumice casts, 99-275A, B, from pumiceous gravels, 0.4 km SSE of KHS, and from two pumice clasts 99-274A, B, 0.5 km SE of KHS, all from Member III, Kibish Formation, Ethiopia. (DOC 145 kb)

Rights and permissions

Reprints and Permissions

About this article

Cite this article

McDougall, I., Brown, F. & Fleagle, J. Stratigraphic placement and age of modern humans from Kibish, Ethiopia. Nature 433, 733–736 (2005).

Download citation

  • Received:

  • Accepted:

  • Issue Date:

  • DOI:

This article is cited by


By submitting a comment you agree to abide by our Terms and Community Guidelines. If you find something abusive or that does not comply with our terms or guidelines please flag it as inappropriate.


Quick links

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