Post by Admin on May 21, 2022 21:19:02 GMT
External and internal structural analyses of the tooth
Externally, the TNH2-1 crown displays a coarse wrinkling pattern that is found in Pleistocene Homo (H. erectus s.l., European and Asian Middle Pleistocene Homo and Neanderthals), but is rare in modern H. sapiens. The mid-trigonid crest is well developed as commonly recorded in European Middle Pleistocene Homo and Neanderthals, while it is generally absent or less frequent in H. erectus s.l. and fossil and extant H. sapiens37. Below the external surface, the enamel-dentine junction (EDJ) of the tooth shows the dentine horns of the five main cusps and of a tuberculum intermedium and a low but uninterrupted mid-trigonid crest (Figs. 2 and 3, Supplementary Fig. 2; Methods). The latter feature is generally found in Neanderthals (80–100% depending on the molar position)38,39,40 but is less frequent in H. erectus s.l. and H. sapiens41,42,43,44,45,46,47 (Supplementary Fig. 5). In addition, the EDJ of TNH2-1 shows an internally-positioned metaconid reminiscent of Neanderthal molars40 and a low crown topography similar to that of H. erectus41,42,43,44,45,46,47. These features, as well as a slight buccal shelf present on the EDJ of TNH2-1, are all expressed on the EDJ of the Denisovan molars from Baishiya Karst Cave (Xiahe, Gansu, China) (Supplementary Fig. 5)15. TNH2-1 dentine differs from the much higher and proportionally more mesiodistally compressed EDJ of Neanderthals and H. sapiens39,40, as well as from the shorter dentine horns and more densely wrinkled occlusal basin of H. erectus s.l.41,42,43,44,45,46,47 (Supplementary Fig. 5).
Fig. 3: Morphological features on the virtual rendering of the TNH2-1 specimen.
In terms of absolute dimensions, only Asian Middle Pleistocene Homo have larger tooth crowns than TNH2-1 (Supplementary Tables 9, 10). TNH2-1 crown metrics are within the ranges of variation for H. erectus s.l., H. antecessor, Asian Middle Pleistocene Homo and Neanderthals, but they statistically differ from the smaller crowns of European Middle Pleistocene Homo and from Pleistocene and Holocene H. sapiens (Fig. 4; Supplementary Tables 10, 11). With respect to tooth crown tissue proportions, TNH2-1 has a high percentage of crown dentine (Vcdp/Vc: 55.37%) with moderately thick enamel as shown by absolute and relative enamel thickness values (3D AET: 1.18 mm; 3D RET: 17.00; Supplementary Table 12). These crown tissue proportions match to those of the nearly unworn M2 of the Xiahe mandible15 (Vcdp/Vc: 54.62%; 3D AET: 1.47 mm; 3D RET: 18.97) and the upper molar of Denisova 4 (3D RET: 15.27; B. Viola, pers. comm.), but within the ranges of variation of all comparative fossil and extant human groups (Supplementary Fig. 6a–c; Supplementary Tables 12, 13). Three-dimensional maps of topographic enamel thickness distribution show that TNH2-1 has the thickest enamel at the top of the hypoconid and hypoconulid cusps and in the distobuccal quarter of the crown (Supplementary Fig. 6d). In comparison, all other samples tend to have the thickest enamel distributed on all buccal cusps and more spread on the buccal aspect of the crown, even if variable between groups and between molar positions. The M2 of the Xiahe specimen shows thicker enamel spread along the buccal crown aspect but its distribution pattern is partly obliterated by occlusal wear.
Externally, the TNH2-1 crown displays a coarse wrinkling pattern that is found in Pleistocene Homo (H. erectus s.l., European and Asian Middle Pleistocene Homo and Neanderthals), but is rare in modern H. sapiens. The mid-trigonid crest is well developed as commonly recorded in European Middle Pleistocene Homo and Neanderthals, while it is generally absent or less frequent in H. erectus s.l. and fossil and extant H. sapiens37. Below the external surface, the enamel-dentine junction (EDJ) of the tooth shows the dentine horns of the five main cusps and of a tuberculum intermedium and a low but uninterrupted mid-trigonid crest (Figs. 2 and 3, Supplementary Fig. 2; Methods). The latter feature is generally found in Neanderthals (80–100% depending on the molar position)38,39,40 but is less frequent in H. erectus s.l. and H. sapiens41,42,43,44,45,46,47 (Supplementary Fig. 5). In addition, the EDJ of TNH2-1 shows an internally-positioned metaconid reminiscent of Neanderthal molars40 and a low crown topography similar to that of H. erectus41,42,43,44,45,46,47. These features, as well as a slight buccal shelf present on the EDJ of TNH2-1, are all expressed on the EDJ of the Denisovan molars from Baishiya Karst Cave (Xiahe, Gansu, China) (Supplementary Fig. 5)15. TNH2-1 dentine differs from the much higher and proportionally more mesiodistally compressed EDJ of Neanderthals and H. sapiens39,40, as well as from the shorter dentine horns and more densely wrinkled occlusal basin of H. erectus s.l.41,42,43,44,45,46,47 (Supplementary Fig. 5).
Fig. 3: Morphological features on the virtual rendering of the TNH2-1 specimen.
In terms of absolute dimensions, only Asian Middle Pleistocene Homo have larger tooth crowns than TNH2-1 (Supplementary Tables 9, 10). TNH2-1 crown metrics are within the ranges of variation for H. erectus s.l., H. antecessor, Asian Middle Pleistocene Homo and Neanderthals, but they statistically differ from the smaller crowns of European Middle Pleistocene Homo and from Pleistocene and Holocene H. sapiens (Fig. 4; Supplementary Tables 10, 11). With respect to tooth crown tissue proportions, TNH2-1 has a high percentage of crown dentine (Vcdp/Vc: 55.37%) with moderately thick enamel as shown by absolute and relative enamel thickness values (3D AET: 1.18 mm; 3D RET: 17.00; Supplementary Table 12). These crown tissue proportions match to those of the nearly unworn M2 of the Xiahe mandible15 (Vcdp/Vc: 54.62%; 3D AET: 1.47 mm; 3D RET: 18.97) and the upper molar of Denisova 4 (3D RET: 15.27; B. Viola, pers. comm.), but within the ranges of variation of all comparative fossil and extant human groups (Supplementary Fig. 6a–c; Supplementary Tables 12, 13). Three-dimensional maps of topographic enamel thickness distribution show that TNH2-1 has the thickest enamel at the top of the hypoconid and hypoconulid cusps and in the distobuccal quarter of the crown (Supplementary Fig. 6d). In comparison, all other samples tend to have the thickest enamel distributed on all buccal cusps and more spread on the buccal aspect of the crown, even if variable between groups and between molar positions. The M2 of the Xiahe specimen shows thicker enamel spread along the buccal crown aspect but its distribution pattern is partly obliterated by occlusal wear.