Hand to Mouth in a Neandertal: Right-Handedness in Regourdou 1

Abstract

We describe and analyze a Neandertal postcranial skeleton and dentition, which together show unambiguous signs of right-handedness. Asymmetries between the left and right upper arm in Regourdou 1 were identified nearly 20 years ago, then confirmed by more detailed analyses of the inner bone structure for the clavicle, humerus, radius and ulna. The total pattern of all bones in the shoulder and arm reveals that Regourdou 1 was a right-hander. Confirmatory evidence comes from the mandibular incisors, which display a distinct pattern of right oblique scratches, typical of right-handed manipulations performed at the front of the mouth. Regourdou's right handedness is consistent with the strong pattern of manual lateralization in Neandertals and further confirms a modern pattern of left brain dominance, presumably signally linguistic competence. These observations along with cultural, genetic and morphological evidence indicate language competence in Neandertals and their European precursors.

Humeral laterality in modern humans and Neanderthals: a 3D geometric morphometric analysis

“…Neanderthals have been determined to be right-handed by different methodologies (LeMay, 1976;Holloway and De La Coste-Lareymondie, 1982;Trinkaus et al, 1994;Vandermeersch and Trinkaus, 1995) with an approximate ratio of 90% Uomini, 2011;Volpato et al, 2012). This proportion is very similar to that found in modern human populations, which ranges from 70% to 98% (Perelle and Ehrman, 1994;Marchant and McGrew, 1998;Faurie et al, 2005; among others).…”

“…All of these Neanderthal individuals are considered to be male (Trinkaus, 1980), and righthanded based on humeral laterality studies (Trinkaus et al, 1994;Uomini, 2011;Volpato et al, 2012).…”

“…This may be due to the fragmentary state of the fossils, or because of the intrinsic difficulty in assigning isolated upper-limb remains to the same individual. One of the most studied Neanderthal specimens is Régour-dou 1, and both the upper-limb analysis (Vandermeersch and Trinkaus, 1995;Volpato et al, 2012) and dentition (Volpato et al, 2012) suggest that this individual was right-handed. Furthermore, Trinkaus et al (1994) studied humeral laterality in eight Neanderthal individuals, observing that the right humeri are larger than the left humeri.…”

“…All of these studies concluded that Neanderthals were mostly right-handed; there are only three Neanderthal individuals considered lefthanded: an individual from Krapina (KDP 4), Hortus (Hortus VII) , and Vergisson 4 (Vg 4-83) (Condemi et al, 2017). Thus, with a total of 27 right-handed and 3 left-handed individuals, Neanderthals demonstrate very similar proportions of right-handedness to modern humans (Uomini, 2011;Volpato et al, 2012;Condemi et al, 2017).…”

Inner structural organization of the distal humerus in Paranthropus and Homo

“…differential structural reinforcements of the diaphysis (Ruff, 2008;Trinkaus and Ruff, 2012). Accordingly, even if we cannot discard here the possible influence on the endostructural bony arrangement of sex-related (or even of age-related) differences, nor that of a different handedness (for a recent discussion on hand specialization in early Homo, see Frayer et al, 2016; for its impact on humeral cross-sectional shape variation and cortical bone thickness distribution, see Lague, 2015 andVolpato et al, 2012, respectively), we anyhow assume that the two distinct conditions ("patterns") revealed by the South African and the Ethiopian specimens, whatever their taxonomic status, are primarily functionally-related and have biomechanical significance in terms of distal humeral strength.…”