How old is the Montmaurin-La Niche hominin mandible in the Middle Pleistocene? A state of the question
Résumé
The hominin mandible known as La Niche (LN) has been famous since its discovery by R. Cammas, on 18 June 1949, in a small
cavity uncovered by the exploitation of a quarry in the Montmaurin limestone massif, south-west of Toulouse and in the context of
the Pyrenean piedmont. H.-V. Vallois and G. Billy had highlighted the archaic characters of this fossil [1] which we have re-examined,
considering an increased fossil record since the 1970s and analysing the internal dental features now accessible [2-3]. On the basis of
the faunal remains and lithic tools collected, Cammas [4] argued an in situ position of this material and a stratigraphy of the infilling
composed by 3 main levels (B-C1-C3), with the mandible and three other human remains from the deepest level (C3). Later, based
on biochronology of the mammals, an attribution to marine isotopic stage 7 (i.e., between 250 and 190 ka) was proposed [5].
However, the history of the deposits is complex and the possibility of archaeological material in a secondary position is not
excluded. It could indeed be the result of the extraction of elements from the upper karst level situated at 40m high overlying the LN
chimney 12m.
To test this hypothesis, as part of an ongoing multi-disciplinary project, we carried out a pit at LN, through the spoil from the
old excavations, to reach the clay level in situ, about 1.40m below the level of the mandible. This level has been dated by the
cosmogenic nuclide method applied on a quartzite flake. In addition, dates were obtained for levels C3 and C1 using ESR/U-series
on herbivorous teeth. In parallel, the geological processes that could explain the history of this infilling were clarified by analysis of
the clay minerals.
All these results are discussed here in an attempt to constrain the chronological interval of the C3 level bearing the human remains.
It should be remembered that the mandible combines archaic features such as a marked planum alveolare, downward located fossae
digastrica, a sub-parallel mylohyoid line, a deep pterygoid fossa or a regular gonion profile with some neandertal traits like a well-
marked fovea anterior and a mid-trigonid crest on M1, M2, M3. As a result, it seems that the Montmaurin-LN mandible is not fully
neandertal. An earlier dating than the MIS 7 as previously proposed would have been consistent with its primitive state. If a more
recent dating is confirmed, it should be considered that this famous fossil represents a primitive specimen at a time of the emergence
of the Neandertal lineage. This may correspond to the coexistence of two or more populations during the late Middle Pleistocene in
Europe, one being more primitive than the others.
Acknowledgements to the French Ministry of Culture (DRAC
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