Determinants of retromolar space presence in Pleistocene Homo mandibles

Hominin lower second premolar morphology: evolutionary inferences through geometric morphometric analysis

“…Our findings are consistent with the hypothesis that Neandertals are the result of a process of character accretion which started during the Middle Pleistocene Hublin, 1998). In this view, some of the morphological traits considered to be typical of Neandertals are not Neandertal apomorphies but instead are distinctive combinations of symplesiomorphic characters (Patte, 1962;Franciscus and Trinkaus, 1995). For example, we find that H. heidelbergensis/neanderthalensis apparently show a distinctive combination of primitive dental traits (asymmetrical contour, mesially displaced metaconid, and extra lingual cusps) in association with other traits like a well-developed transverse ridge (Bailey, 2002a,b;Bailey and Lynch, 2005) (Fig.…”

Morphological description and comparison of the dental remains from Atapuerca-Sima de los Huesos site (Spain)

“…It could indicate that those traits are indeed synapomorphies inherited from a hypothetical last common ancestor, and that those traits would eventually be lost in H. sapiens while they became typical of H. neanderthalensis. In this context, many of the "typical Neanderthal" traits would not be Neanderthal apomorphies but distinctive combinations of primitive features (see also Patte, 1962;Franciscus and Trinkaus, 1995;Bailey, 2002a,b;Martinon-To rres et al, 2006) present in the hominin record prior to the Neanderthal and H. sapiens divergence. Alter natively, the Qafzeh hominins could be the result of a hybridization process between early H. sapiens and H. neanderthalensis in the Middle East, as it has been already posited by the archaeological and molecular data (Bar-Yosef, 1994;Green et al, 2010).…”

“…Thus, H. heidelbergensis could be defined by a combination of primitive traits (plesiomor phies) not fo und in later Neanderthals, incipient Neanderthal-like traits (mesomorphies), and typical Neanderthal traits (apomor phies) (Arsuaga et al, 1997c). It has also been suggested that many of the so-called typical Neanderthal traits are not Neanderthal autapomorphies but primitive fe atures that, because of their high frequencies and degrees of expression, and their distinctive combination, become typical of H. neanderthalensis species (e.g., Patte, 1962;Franciscus and Trinkaus, 1995;Bailey, 2002a;Martinon-Torres et al, 2006;Bailey et al, 2009;Hublin, 2009). Thus, the origin of the Neanderthal lineage would imply increasing frequencies of Neanderthal traits throughout time, favored by isolation due to glacial conditions (Arsuaga et al, 1993;Hublin, 1996Hublin, , 1998Dean et al, 1998).…”

Influence of the Interproximal Attrition of Teeth on the Formation of Neanderthal Retromolar Space.

“…As summarized by Franciscus and Trinkaus (1995), several explanations relating the variation in Neanderthal dentofacial morphology to the high frequency of retromolar space have been put forward (Coon, 1962;Howells, 1975;Rak, 1986;Trinkaus, 1987;Spencer and Demes, 1993;Franciscus and Trinkaus, 1995). These arguments emphasize that some selective forces that produce the prognathic facial features have worked in particular fashion for the formation of retromolar space of the Neanderthals.…”

“…More recently, Spencer and Demes (1993) argued that an apparent separation of the masticatory muscles relative to the molar dentition suggested by the retromolar space was interpreted as the result of differential anterior migration of the molars and the masseter and temporalis muscles in terms of the efficiency of producing forces on the anterior dentition. Franciscus and Trinkaus (1995) demonstrated that the retromolar space was best seen as a combined result of the reduced dental arcade length and the reduced ramus breadth in the context of little reduction in overall mandibular length.…”