Homo sapiens idaltu
The fossilized remains of H. s. idaltu were discovered at Herto Bouri in the Middle Awash site of Ethiopia's Afar Triangle in 1997 by Tim White, but were first unveiled in 2003. Herto Bouri is a region of Ethiopia under volcanic layers. By using radioisotope dating, the layers date between 154,000 and 160,000 years old. Three well preserved crania are accounted for, the best preserved being from an adult male (BOU-VP-16/1) having a brain capacity of 1,450 cm3 (88 cu in). The other crania include another partial adult male and a six year old child.
These fossils differ from those of chronologically later forms of early H. sapiens such as Cro-Magnon found in Europe and other parts of the world in that their morphology has many archaic features not typical of H. sapiens (although modern human skulls do differ across the globe).
Despite the archaic features, these specimens were argued to represent the direct ancestors of modern Homo sapiens sapiens which, according to the "recent African origin (RAO)" or "out of Africa" theory, developed shortly after this period (Khoisan mitochondrial divergence dated not later than 110,000 BCE) in Eastern Africa. "The many morphological features shared by the Herto crania and AMHS, to the exclusion of penecontemporanous Neanderthals, provide additional fossil data excluding Neanderthals from a significant contribution to the ancestry of modern humans."
A 2005 potassium-argon dating of volcanic tuff associated with the Omo remains showed them to date from about 195,000 years ago, making them older than the idaltu fossils and the earliest known remains of anatomically modern humans.
An exact description was made, by its discoverers, of Homo sapiens idaltu.
"On the limited available evidence, a subspecies of Homo sapiens distinguished from Holocene anatomically modern humans (Homo sapiens sapiens) by greater craniofacial robusticity, greater anterior–posterior cranial length, and large glenoid-to-occlusal plane distance. Homo sapiens idaltu is distinguished from the holotype of Homo rhodesiensis (Woodward, 1921) by a larger cranial capacity, a more vertical frontal with smaller face, and more marked midfacial topography (for example, canine fossa). We consider the holotypes of H. helmei and H. njarasensis too fragmentary for appropriate comparisons."
- ^ a b c d e f g White, Tim D.; Asfaw, B.; DeGusta, D.; Gilbert, H.; Richards, G. D.; Suwa, G.; Howell, F. C. (2003), "Pleistocene Homo sapiens from Middle Awash, Ethiopia", Nature 423 (6491): 742–747, doi:10.1038/nature01669, PMID 12802332
- ^ McDougall, I.; Brown, F. H.; Fleagle, J. G. (2005), "Stratigraphic placement and age of modern humans from Kibish, Ethiopia", Nature 433 (7027): 733–736, doi:10.1038/nature03258, PMID 15716951