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Human Origins Leiden

New article: On the Variability of the Dmanisi Mandibles

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Authors: José María Bermúdez de Castro, María Martinón-Torres, Mark Jan Sier, Laura Martín-Francés

Abstract
The description of a new skull (D4500) from the Dmanisi site (Republic of Georgia) has reopened the debate about the
morphological variability within the genus Homo. The new skull fits with a mandible (D2600) often referred as ‘big’ or
‘enigmatic’ because of its differences with the other Dmanisi mandibles (D211 and D2735). In this report we present a
comparative study of the variability of the Dmanisi mandibles under a different perspective, as we focus in morphological
aspects related to growth and development. We have followed the notion of modularity and phenotypic integration in
order to understand the architectural differences observed within the sample. Our study reveals remarkable shape
differences between D2600 and the other two mandibles, that are established early in the ontogeny (during childhood or
even before) and that do not depend on size or sexual dimorphism. In addition, D2600 exhibits a mosaic of primitive and
derived features regarding the Homo clade, which is absent in D211 and D2735. This mosaic expression is related to the
location of the features and can be explained under the concept of modularity. Our study would support the possibility of
two different paleodemes represented at the Dmanisi site. This hypothesis has been previously rejected on the basis that all
the individuals were constrained in the same stratigraphic and taphonomic settings. However, our revision of the complex
Dmanisi stratigraphy suggests that the accumulation could cover an undetermined period of time. Even if ‘‘short’’ in
geological terms, the hominin accumulation was not necessarily synchronic. In the same line we discard that the differences
between D2600 and the small mandibles are consequence of wear-related dentoalveolar remodeling. In addition, dental
wear pattern of D2600 could suggest an adaptation to a different ecological niche than the other Dmanisi individuals.

Link to article: http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0088212

mandibles

 

New paper: Improved age control on early Homo fossils from the upper Burgi Member at Koobi Fora, Kenya

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Authors: Josephine Joordens, Guillaume Dupont-Nivet, Craig Feibel, Fred Spoor, Mark Sier, Jeroen van der Lubbe, Trine Kellberg Nielsen, Monika Knul, Gareth Davies, Hubert Vonhof

Journal: Journal of Human Evolution

Fieldwork 2010_resized


Abstract: To address questions regarding the evolutionary origin, radiation and dispersal of the genus Homo, it is crucial to be able to place the occurrence of hominin fossils in a high-resolution chronological framework. The period around 2 Ma (millions of years ago) in eastern Africa is of particular interest as it is at this time that a more substantial fossil record of the genus Homo is first found. Here we combine magnetostratigraphy and strontium (Sr) isotope stratigraphy to improve age control on hominin-bearing upper Burgi (UBU) deposits in Areas 105 and 131 on the Karari Ridge in the eastern Turkana Basin (Kenya). We identify the base of the Olduvai subchron (bC2n) plus a short isolated interval of consistently normal polarity that we interpret to be the Pre-Olduvai event. Combined with precession-forced (~ 20 kyr [thousands of years]) wet-dry climate cycles resolved by Sr isotope ratios, the magnetostratigraphic data allow us to construct an age model for the UBU deposits. We provide detailed age constraints for 15 hominin fossils from Area 131, showing that key specimens such as cranium KNM-ER 1470, partial face KNM-ER 62000 and mandibles KNM-ER 1482, KNM-ER 1801, and KNM-ER 1802 can be constrained between 1.945 ± 0.004 and 2.058 ± 0.034 Ma, and thus older than previously estimated. The new ages are consistent with a temporal overlap of two species of early Homo that can be distinguished by their facial morphology. Further, our results show that in this time interval, hominins occurred throughout the wet-dry climate cycles, supporting the hypothesis that the lacustrine Turkana Basin was a refugium during regionally dry periods. By establishing the observed first appearance datum of a marine-derived stingray in UBU deposits at 2.058 ± 0.034 Ma, we show that at this time the Turkana Basin was hydrographically connected to the Indian Ocean, facilitating dispersal of fauna between these areas. From a biogeographical perspective, we propose that the Indian Ocean coastal strip should be considered as a possible source area for one or more of the multiple Homo species in the Turkana Basin from over 2 Ma onwards.

 

Neandertals made the first specialized bone tools in Europe

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Figure 5_-_AP_Lissoir__AP__PAI_projects_400New finds demonstrate that Neandertals were the first in Europe to make standardized and specialized bone tools – which are still in use today.

Two research teams from the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, and the University of Leiden in the Netherlands have jointly reported the discovery of Neandertal bone tools coming from their excavations at two neighboring Paleolithic sites in southwest France. The tools are unlike any others previously found in Neandertal sites, but they are similar to a tool type well known from later modern human sites and still in use today by high-end leather workers. This tool, called a lissoir or smoother, is shaped from deer ribs and has a polished tip that, when pushed against a hide, creates softer, burnished and more water resistant leather. The bone tool is still used today by leather workers some 50 thousand years after the Neandertals and the first anatomically modern humans in Europe.

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