Sapropels and the age of hominins Omo I and II, Kibish, Ethiopia

The provenance and age of two Homo sapiens fossils (Omo I and Omo II) from the Kibish Formation in southern Ethiopia have been much debated. Here we confirm that Omo I and the somewhat more primitive-looking Omo II calvariae are from similar stratigraphic levels in Member I of the Kibish Formation....

Full description

Saved in:
Bibliographic Details
Published in:Journal of human evolution 2008-09, Vol.55 (3), p.409-420
Main Authors: McDougall, Ian, Brown, Francis H., Fleagle, John G.
Format: Article
Language:English
Subjects:
40Ar/ 39Ar dating
Aluminum Silicates - analysis
Animals
Archaeological dating
Archaeological sites
Argon - analysis
Benzopyrans - analysis
Ethiopia
Eukaryota - chemistry
Fossils
Geologic Sediments - analysis
History, Ancient
Hominids
Human remains
Humans
Humic Substances - analysis
Kibish Formation
Mediterranean Region
Mediterranean sapropels
Modern hominins
Potassium Compounds - analysis
Radiometric Dating
Sea
Soils
Tephrostratigraphy
Time Factors
Citations: Items that this one cites
Items that cite this one
Online Access:Get full text
Tags: Add Tag
No Tags, Be the first to tag this record!
Description
Summary:The provenance and age of two Homo sapiens fossils (Omo I and Omo II) from the Kibish Formation in southern Ethiopia have been much debated. Here we confirm that Omo I and the somewhat more primitive-looking Omo II calvariae are from similar stratigraphic levels in Member I of the Kibish Formation. Based on 40Ar/ 39Ar age measurements on alkali feldspar crystals from pumice clasts in the Nakaa'kire Tuff, a tuffaceous bed in Member I just below the hominin levels, we place an older limit of 198 ± 14 ka (weighted mean age = 196 ± 2 ka) for the hominins. A younger limit of 104 ± 7 ka (weighted mean age = 104 ± 1 ka) is provided by feldspars separated from pumice clasts in the Aliyo Tuff in Member III. Geological evidence indicates rapid deposition of each member of the Kibish Formation, concurrent with deposition of sapropels in the Mediterranean Sea. The 40Ar/ 39Ar age measurements, together with correlations with sapropels, indicate that the hominin fossils are close in age to the older limit. Our preferred estimate of the age of the hominins is 195 ± 5 ka, making them the earliest well-dated anatomically modern humans yet described.
ISSN:0047-2484
1095-8606
DOI:10.1016/j.jhevol.2008.05.012