Supplementary Information

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1 Supplementary Information Materials. The deciduous (S14-5) and permanent (BD-J4-C9) Neanderthal molars used in this study are isolated specimens from La Chaise-de-Vouthon, Charente, France. The site (0 26'48" E, 45 40'13" N) consists of two major rock shelters/caves: the Abri Suard, whose deposit dates from Riss II to Riss-Würm, and the Abri Bourgeois- Delaunay, dated from Riss III to Würm III (Debénath 1974; Blackwell et al. 1983, 1992). Recently, a new set of 230 Th/ 234 U speleothem dates have been realized by Thermal Ionization Mass Spectrometry (TIMS) at the GEOTOP center set at the Univ. of Québec, Montréal. Accordingly, the human remains from the Abri Suard - all from OIS 6 (Riss III) - are younger than 163 kyr, while the age of those from Bourgeois- Delaunay - OIS 5e (Eemian) - is comprised between 127 and 116 kyr (I. Couchoud & B. Ghaleb, 2006, pers. comm.). Discovered in 1850, the site was extensively excavated between 1930 and 1963 by P. David and between 1967 and 1983 by A. Debénath (in Debénath 2006). La Chaise has provided a human fossil sample consisting of 75 subadult and adult Neanderthal remains (52 from Suard and 23 from Bourgeois- Delaunay), including a number of isolated teeth (Genet-Varcin 1974, 1975a, b, 1976; Legoux 1976; Debénath 1977; Tillier & Genet-Varcin 1980; Piveteau et al. 1982; Condemi 2001; Teilhol 2001, 2003). S14-5 is a lower right deciduous second molar (LRm2) from Suard (Suppl. Fig. 1); BD-J4-C9 is a lower left permanent first molar (LLM1) from Bourgeois-Delaunay (Suppl. Fig. 2). Both crowns show only slight occlusal wear. Based on the high-resolution synchrotron radiation micro-ct record (SR-µCT), a set of 49 linear, curvilinear, surface, and volumetric variables digitally measured on each tooth (Suppl. Fig. 3) are provided in Suppl. Table 1. Root extension rates. Continuous data were collected along the whole permanent M1 root length in 20 modern human teeth of southern African origin (Reid & Dean 2006) and in the Neanderthal (BD-J4-C9) from La Chaise (Suppl. Fig. 4, Suppl. Fig. 5) using a montage of photomicrographs taken in transmitted polarized light with a Zeiss Jenamed microscope (x 25 objective). Dentine tubules (Suppl. Fig. 4) were then traced from the root surface just beneath the last formed enamel at the cervix (point A) to a 1

2 point 200 microns along dentine tubules into root dentine (point B). This thickness of dentine forms at an average rate of 2.5 microns/day and takes ca 80 days to form (Dean 1998). Accentuated markings (Owen s lines and/or Andresen lines) were identified in the region of point B running obliquely back towards the root surface (Suppl. Fig. 4). A line parallel with their orientation was drawn from point B back to the root surface (point C). The distance between point A and point C represents the length by which the root had extended in ca 80 days. An extension rate was calculated in microns/day for this distance along the root. This procedure was then repeated such that point C became point A in each calculation along the length of the whole root. Cited references Blackwell, B. A., Porat, N., Schwarcz, H. P. & Debénath, A. ESR dating of tooth enamel: comparison with 230 Th/ 234 U speleothem dates at La Chaise-de-Vouthon (Charente), France. Quat. Sci. Rev. 11, (1992). Blackwell, B. A., Schwarcz, H. P. & Debénath, A. Absolute dating of hominids and Paleolithic artefacts of the cave of La Chaise-de-Vouthon (Charente), France. J. Archaeol. Sci. 10, (1983). Condemi, S. Les Néanderthaliens de La Chaise (Abri Bourgeois-Delaunay) (CTHS, Paris, 2001). Dean, M. C. Comparative observations on the spacing of short-period (von Ebner s) lines in dentine. Archs. Oral Biol. 43, (1998). Debénath, A. Recherches sur les Terrains Quaternaires des Charents et les Industries qui leur sont Associées («Doctorat d Etat» dissertation, Université de Bordeaux I, Bordeaux, 1974). Debénath, A. The latest finds of antewürmien human remains in Charente (France). J. Hum. Evol. 6, (1977). Debénath, A. Néanderthaliens et Cro-Magnons. Les Temps Glaciaires dans le Bassin de la Charente (Le Croît Vif, Paris, 2006). Genet-Varcin, E. Etude des dents humaines isolées provenant des grottes de la Chaisede-Vouthon (Charente). Bull. Mém. Soc. Anthropol. Paris 1, (1974). 2

3 Genet-Varcin, E. Etude des dents humaines isolées provenant des grottes de la Chaisede-Vouthon (Charente). Bull. Mém. Soc. Anthropol. Paris 2, (1975a). Genet-Varcin, E. Etude des dents humaines isolées provenant des grottes de la Chaisede-Vouthon (Charente). Bull. Mém. Soc. Anthropol. Paris 2, (1975b). Genet-Varcin, E. Etude des dents humaines isolées provenant des grottes de la Chaisede-Vouthon (Charente). Bull. Mém. Soc. Anthropol. Paris 3, (1976). Gleiser, I. & Hunt, E. E. The permanent mandibular molar: Its clacification, eruption and decay. Am. J. Phys. Anthropol. 13, (1955). Legoux, P. Les dents de La Chaise-de-Vouthon. Etude pathologique et radiologique. Bull. Mém. Soc. Anthropol. Paris 3, (1976). Piveteau, J., de Lumley, M.-A. & Debénath, A. in 1 er Congrès International de Paléontologie Humaine (ed de Lumley, H.) (C.N.R.S., Nice, 1982). Reid, D. J. & Dean, M. C. Variation in modern human enamel formation times. J. Hum. Evol. 50, (2006). Teilhol, V. Contribution à l Etude Individuelle des Ossements d Enfants de La Chaisede-Vouthon (Charente, France): Approche Paléodémographique, Paléoethnologique, Aspect Morphologique et Etude Métrique. Place Phylogénique des Enfants de La Chaise (PhD dissertation, Université de Perpignan, Perpignan, 2001). Teilhol, V. Les os de la voûte crânienne des enfants de l abri Suard (La Chaise, Charente, France). C.R. Palevol 2, (2003). Tillier, A.-M. & Genet-Varcin, E. La plus ancienne mandibule d enfant découverte en France dans le gisement de La Chaise de Vouthon (Abri Suard) en Charente. Z. Morph. Anthrop. 71, (1980). 3

4 Supplementary Figure 1 The deciduous molar, S14-5, from La Chaise. LRm2 in occlusal (centre), mesial (top), distal (bottom), lingual (left), and buccal (right) views. Scale bar, 2 mm. 4

5 Supplementary Figure 2 The permanent molar, BD-J4-C9, from La Chaise. LLM1 in occlusal (centre), mesial (top), distal (bottom), buccal (left), and lingual (right) views. Scale bar, 2 mm. 5

6 Supplementary Figure 3 Micro-CT-based (SR-µCT) 3D virtual reconstruction of deciduous and permanent Neanderthal molars from La Chaise (buccal view). a, S14-5 (LRm2). b, BD-J4-C9 (LLM1). The original 3D volumes have been segmented in order to differentiate the enamel cap (upper, white), the dentine (centre, gold), the pulp chamber and the root canals (lower, red). Scale bar for the two complete teeth, 2 mm. 6

7 Supplementary Figure 4 Transmitted light micrograph of mesiobuccal root dentine in BD-J4-C9 (LLM1). Incremental markings can be seen oriented obliquely to the root surface in the direction of the arrow. Point B is 200 microns from point A (or ~80 days). Dentine tubules are running from the root surface parallel with a line between A and B. Scale bar, 50 µm. 7

8 Supplementary Figure 5 Change in extension rates over the length of the growing root in the Neanderthal M1 from La Chaise compared with data from a sample of 20 modern humans. The peak or spurt in root extension rate occurs in modern humans at about the time the root bifurcation begins to form (Gleiser & Hunt 1955). The peak in the Neanderthal occurs later, towards the end of root formation. 8

9 Supplementary Table 1 Micro-CT-based (SR-µCT) 2-3D digital measurements of S14-5 (LRm2) and BD-J4-C9 (LLM1) Neanderthal teeth from La Chaise, and selected comparative 3D measurements performed on a modern human lower m2 (mod. m2) and a lower M1 (mod. M1). Measurements S14-5 BD-J4-C9 2D measurements based on the virtual cross-section through metaconid-protoconid (mesial) total area of the crown section a (mm 2 ) area of dentine and pulp enclosed within the enamel cap b (mm 2 ) area of the sectioned enamel cap c (mm 2 ) linear distance between the buccal and lingual cervical margins (bicervical diameter) d (mm) perimeter length of the EDJ e (mm) maximum linear thickness of occlusal enamel on the protoconid f (mm) maximum linear thickness of occlusal enamel on the mid-occlusal basin g (mm) maximum linear thickness of occlusal enamel on the metaconid h (mm) maximum linear enamel thickness on the buccal side of the protoconid I (mm) maximum linear enamel thickness on the lingual side of the metaconid j (mm) linear enamel thickness on the apex of the protoconid k (mm) linear enamel thickness on the apex of the metaconid l (mm) average enamel thickness of the crown section m (mm) relative enamel thickness of the crown section n D measurements based on the virtual cross-section through entoconid-hypoconid (distal) total area of the crown section (mm 2 ) area of dentine and pulp enclosed within the enamel cap (mm 2 ) area of the sectioned enamel cap (mm 2 ) linear distance between the buccal and lingual cervical margins (bicervical diameter) (mm) perimeter length of the EDJ (mm) maximum linear thickness of occlusal enamel on the hypoconid (mm) maximum linear thickness of occlusal enamel on the mid-occlusal basin (mm) maximum linear thickness of occlusal enamel on the entoconid (mm) maximum linear enamel thickness on the buccal side of the hypoconid (mm)

10 maximum linear enamel thickness on the lingual side of the entoconid (mm) linear enamel thickness on the apex of the hypoconid (mm) linear enamel thickness on the apex of the entoconid (mm) average enamel thickness of the crown section (mm) relative enamel thickness of the crown section D measurements based on 3D virtual reconstructions maximum tooth height (projective distance) (mm) maximum crown height (projective distance) (mm) maximum crown mesiodistal diameter (projective distance) (mm) maximum crown buccolingual diameter (projective distance) (mm) maximum root length (projective distance) (mm) total tooth surface (mm 2 ) mod. m2 mod. M1 total crown surface (mm 2 ) total root surface (mm 2 ) total tooth volume (mm 3 ) total crown volume (mm 3 ) total root volume (mm 3 ) total volume of the enamel tissue o (mm 3 ) total volume of crown dentine p (mm 3 ) total volume of the dentine (mm 3 ) total volume of the pulp (mm 3 ) total volume of the pulp chamber (lower limit set at the floor to furcation) q (mm 3 ) surface area of EDJ r (mm 2 ) average of minimum enamel thickness s (mm) maximum radial enamel thickness (mm) average enamel thickness t (mm) relative enamel thickness u estimation affected by slight occlusal wear (at the protoconid, metaconid, and entoconid). 2 estimation affected by root cracks. a meas. a in Grine,

11 b meas. Darea in Kono, 2004; meas. b in Grine c meas. Earea in Kono, 2004; meas. c in Grine, d meas. d in Grine, e meas. EDJL in Kono, 2004; meas. e in Grine, f meas. h in Grine, g meas. MOB in Olejniczak & Grine, h meas. i in Grine, i meas. LTB in Grine, j meas. LTL in Grine, k meas. CTB in Grine, l meas. CTL in Grine, m meas. 2D AET in Kono, n meas. 2D AETSTD in Kono, 2004; meas. RAET in Grine, o meas. Evol in Kono, p meas. Dvol in Kono, q in Macchiarelli et al., r meas. Dsa in Kono, s meas. AMT in Kono, t meas. AET in Kono, u meas. AETSTD in Kono, References Grine, F. E. Enamel thickness of deciduous and permanent molars in modern Homo sapiens. Am. J. Phys. Anthropol. 126, (2005). Kono, R. T. Molar enamel thickness and distribution patterns in extant great apes and humans: new insights based on 3-dimensional whole crown perspective. Anthropol. Sci. 112, (2004). Macchiarelli, R., Bondioli, L., Falk, D., Faupl, P., Illerhaus, B., Kullmer, O., Richter, W., Said, H., Sandrock, O., Schäfer, K., Urbanek, C., Viola, B. T., Weber, G. W. & Seidler, H. Early Pliocene hominid tooth from Galili, Somali Region, Ethiopia. Coll. Antropol. 28, (2004). Olejniczak, A. J. & Grine, F. E. Assessment of the accuracy of dental enamel thickness measurements using microfocal x-ray computed tomography. Anat. Rec. 288A, (2006). 11