A reassessment of the Montmaurin-La Niche mandible (Haute Garonne, France) in the context of European Pleistocene human evolution

Abstract

We here present a comparative study of the Montmaurin-LN Middle Pleistocene mandible (Haute-Garonne, France). This mandible, of which its right and left molar series are preserved in situ, was found in La Niche cave (Montmaurin’s karst system) in 1949, and was first attributed to the ‘Mindel-Riss’ interglacial (= MIS 9 to 11) based on its geological context. Later studies based on geological and faunal evidence have attributed the Montmaurin-LN mandible to MIS 7. Following a detailed morphological and metric comparative study of the mandible in the 1970s, it was interpreted in the light of a still limited fossil record and the prevailing paradigm back then. Waiting for geochronological studies in the forthcoming years, here we review the main morphological and metrical features of this mandible and its molars, which have been reassessed in the framework of a remarkably enlarged Pleistocene fossil record since the mandible was first described, and our current, more in-depth understanding of human evolution in Europe. Using a selection of mandibular features with potential taxonomic signal we have found that the Montmaurin-LN mandible shares only a few derived traits with Neandertals. Our analyses reveal that this mandible is more closely related to the ancient specimens from the African and Eurasian Early and Middle Pleistocene, particularly due to the presence of primitive features of the Homo clade. In contrast, the external morphology of the molars is clearly similar to that of Neandertals. The results are assessed in the light of the present competing hypotheses used to explain the European hominin fossil record.

A human lower third molar from the Acheulean site of Cueva del Ángel (Lucena, Córdoba, Spain)

“…The presence of a wedge‐shaped cusp 7 (C7) can be distinguished distal to the DTC (grade 2). This cusp is almost constant on M 3 s from SH (Martinón‐Torres et al, 2012), while it is absent in many European MP hominins (Bermúdez de Castro et al, 2019; Compton & Stringer, 2015; Vialet et al, 2018) as well as on most Neanderthal M 3 s (Bailey, 2006a). There is no trace of a deflecting wrinkle.…”

Middle Pleistocene hominin teeth from Biache-Saint-Vaast, France

“…While BSV cranial remains exhibit clear Neanderthal features, the number of primitive features retained by the SH population is higher (Rougier 2003;Arsuaga and Martínez 1997). Similarly, while SH mandibles exhibit a clear Neanderthal pattern (Rosas 2001), the Montmaurin mandible is characterised by a particularly primitive conformation (Vialet et al 2018). The question is whether these two MP groups represent (i) a single population with a high degree of variability or (ii) two distinct paleodemes, understood as "representative of prehistoric populations or lineages acting as portions of dynamic evolutionary units" (Trinkaus 1990) where only the one with clear Neanderthal dental affinities (including SH, Pontnewydd, Fontana Ranuccio, Visogliano, Steinheim, Montmaurin and BSV) can be considered active contributors for the Neanderthal gene pool.…”

“…In this model, the geographical and climatic constrains of Europe constituted a driving force in the demographic dynamics (Dennell et al 2011). Amongst European MP fossils, the Atapuerca-Sima de los Huesos (Spain), Steinheim (Germany), Montmaurin (France), Swanscombe and Pontnewydd (UK) and Fontana Ranuccio and Visogliano (Italy) exhibit in their dentitions a suite of features characteristic of the Neanderthal clade (Bermúdez de Castro et al 2019;Martínez de Pinillos et al 2017Martinón-Torres et al 2012;Vialet et al 2018;Zanolli et al 2018). In other European MP specimens, such as those of Ceprano (Italy), Aroeira (Portugal), Mala Balanica (Serbia) and Arago (France), the Neanderthal affinities are less clear (e.g.…”

New dating of the Matalascañas footprints provides new evidence of the Middle Pleistocene (MIS 9-8) hominin paleoecology in southern Europe

“…The post-MIS 10 European fossil record shows, in general, an increasingly more "classic Neandertal" like morphology (e.g., Biache-Saint-Vaast 62 but see 63 ). Some of the MIS 7 fossil remains (such as Ehringsdorf) are regularly referred to as old Neandertals, but some fossil remains, such as the Montmaurin mandible 64 and the Payre mandible 65 , document the persistence of plesiomorphic features even for these more recent periods. The latter could also reflect the aforementioned mosaic pattern of evolution in which some anatomical regions evolve at different rates.…”