littor...@gmail.com wrote:
Corrections of so-called “savanna” habitats, e.g.
Revised stratigraphy of Area 123, Koobi Fora, Kenya,
and new age estimates of its fossil mammals, including hominins
PN Gathogo & FH Brown 2006 J.hum.Evol.51:471-9
… all hominins … from Paleontol.Coll.Area 123 derive from levels between the KBS Tuff (1.87 Ma) & the Lower Ileret Tuff (1.53 Ma) :
53 m of section below the Lower Ileret Tuff, an interval in which beds vary markedly laterally, esp. those units containing molluscs & algal stromatolites.
https://pubmed.ncbi.nlm.nih.gov/16815529/
Abstract
Recent geologic study shows that all hominins and nearly all other published mammalian fossils from Paleontological Collection Area 123, Koobi Fora,
Kenya,
derive from levels between the KBS Tuff (1.87+/-0.02 Ma) and the Lower Ileret Tuff (1.53+/-0.01 Ma). More specifically, the fossils derive from 53 m of section
below the Lower Ileret Tuff, an interval in which beds vary markedly
laterally,
especially those units containing molluscs and algal stromatolites. The upper Burgi Member (approximately 2.00-1.87 Ma) crops out only in the southwestern part of Area 123. Adjacent Area 110 contains larger exposures of the member, and there the KBS Tuff is preserved as an airfall ash in lacustrine
deposits and
also as a fluvially redeposited ash. We observed no mammalian fossils in
situ in
this member in Area 123, but surface specimens have been documented in
some monographic treatments. Fossil hominins from Area 123 were attributed
to strata above the KBS Tuff in the 1970s, but later they were assigned to strata
below the KBS Tuff (now called the upper Burgi Member). This study
definitively
places the Area 123 hominins in the KBS Member. Most of these hominins are between 1.60 and 1.65 myr in age, but the youngest may date to only 1.53 Ma, and the oldest, to 1.75 Ma. All are 0.15-0.30 myr younger than previously estimated. The new age estimates, in conjunction with published taxonomic attributions of fossils, suggest that at least two species of Homo
coexisted in the
region along with A. boisei until at least 1.65 Ma. Comparison of crania
KNM-ER 1813 and KNM-ER 1470, which were believed to be of comparable age,
is at the focus of the debate over whether Homo habilis sensu lato is in fact composed of two species: Homo habilis and Homo rudolfensis. These two crania are separated in time by approximately 0.25 myr, and therefore, arguments for their conspecificity no longer need to confront the issue of unusually high contemporaneous variation within a single species.
Some day you'll learn to be honest...
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