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www.sciencemag.org/cgi/content/full/science.aaa1343/DC1
Supplementary Materials for
Early Homo at 2.8 Ma from Ledi-Geraru, Afar, Ethiopia Brian Villmoare,* William H. Kimbel,* Chalachew Seyoum, Christopher J. Campisano,
Erin DiMaggio, John Rowan, David R. Braun, J. Ramon Arrowsmith, Kaye E. Reed
*Corresponding author. E-mail: brian.villmoare@unlv.edu (B.V.); wkimbel.iho@asu.edu (W.H.K.)
Published 4 March 2015 on Science Express DOI: 10.1126/science.aaa1343
This PDF file includes:
Text S1 to S3 Figs. S1 to S10 Tables S1 to S7 References (34–47)
Supplementary Text
S1. Materials and Methods For the comparative study of LD 350-‐1, we drew on morphological observations and
metrical data collected over a number of years from original fossils of Australopithecus afarensis (Hadar and Maka, Ethiopia; Laetoli, Tanzania), A. africanus (Sterkfontein and Makapansgat, South Africa), A. sediba (Malapa, South Africa), A. aethiopicus (Omo-‐Shungura Formation, Ethiopia), Kenyanthropus platyops (Lomekwi, West Turkana, Kenya), A. robustus (Swartkrans, Kromdraai, and Drimolen, South Africa), A. boisei (Koobi Fora, Kenya; Omo-‐Shungura Formation, Ethiopia), and early Homo (Koobi Fora, Kenya; Omo-‐Shungura Formation, Ethiopia; Olduvai Gorge, Tanzania; Swartkrans, South Africa). Additional observations were made on casts of early Homo mandibles UR 501 (H. rudolfensis; Malawi), KNM-‐BK 67 (H. erectus; Kenya), and the Zhoukoudian (China) H. erectus sample. Additional comparative data were taken from the literature, as cited.
S2. Preservation of LD 350-‐1 (see text Fig. 2) LD 350-‐1 was recovered in two major pieces, separated by a vertical break through the
corpus at distal M1 level. The break is associated with a lost triangular flake of lateral corpus beneath M1. The two pieces fit together without any signs of displacement. Several tooth crown and root fragments, recovered during dry sieving, were joined to the mandible. The anterior break approximates the midline except superiorly (above the superior transverse torus), where it progressively deviates toward the middle of the LI1 alveolus (see Figure S8). The labial walls of the anterior dental alveoli are broken, preventing accurate measurement of alveolus size.
The canine root is broken obliquely such that the cross section is inferiorly inclined labially. Thus, the area of the root cross section appears (in occlusal view) smaller than it would had the labial section of the root reached the same height as the lingual section. The P3 crown is missing the mesiolingual quadrant and the distolingual corner. A crack slightly separates the mesial and distal halves of the buccal crown (the measured crown length reported here compensates for this separation). The P4 crown, composed of two pieces joining along a mesiodistal break, is complete. The M1 crown is missing the mesiobuccal quadrant and the mesiolingual corner. M2 is intact; two hairline cracks traverse the occlusal surface, one across the mesial cusps the other across the distal cusps (measured crown length compensates for these cracks). The mesial half of the M2 buccal face is chemically etched, but this has not affected the crown contour or dimensions. M3 is intact; a hairline crack splits the hypoconulid and runs over the occlusal margin on to the middle of the distal face.
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S3. Evaluation of alternative systematic hypotheses regarding LD 350-‐1 Here we record background observations on early hominin species and specimens that are relevant to the systematic status of the LD 350-‐1 mandible due to their age and/or previously articulated hypotheses regarding the early evolution of the Homo lineage. 1. Australopithecus garhi Australopithecus garhi (Hata Beds, Bouri, Middle Awash, Ethiopia) is known mainly from a ~2.5 Ma partial cranium (BOU-VP 12/130) with maxillary dentition (25). It is ~0.3 myr younger than the LD 350-‐1 mandible. Asfaw et al. (25) proposed four alternative phylogenetic hypotheses incorporating A. garhi, in three of which it is considered directly ancestral to Homo via anagenesis (in the fourth, it leaves no descendants). In a formal phylogenetic analysis, using data from (25), Strait and Grine (27) found “no support” for a sister group relationship between A. garhi and Homo. Instead, in their most parsimonious cladograms, A. garhi was basal to a clade comprising A. africanus, Kenyanthropus, Paranthropus and Homo. Its greatly enlarged relative P3 size (25, 34) resembles the specialized robust australopith condition, though without the pronounced premolar molarization characteristic of this group. Moreover, at ~2.3 Ma, the A.L. 666-‐1 maxilla (Busidima Formation, Hadar, Ethiopia) displays derived gnathic morphology unambiguously shared exclusively with later Homo (19), which stands in strong contrast to the primitive (A. afarensis-‐like) maxilla of the A. garhi holotype. As Asfaw et al. (25) noted, an A. garhi to Homo evolutionary sequence would imply a very rapid transition from primitive to highly derived facial anatomy. Alternatively, the evidence is consistent with the lack of a close phylogenetic relationship between A. garhi and Homo (as suggested by the fourth hypothesis in 25). The A. garhi holotype is noted for its extremely large dentition, and this is certainly true relative to the teeth of LD 350-‐1 (allowing for an upper to lower dental comparison). To test the hypothesis that LD 350-‐1 represents the same species as A. garhi, we resampled mandibular and maxillary dental size data from samples of wild-‐shot Pan troglodytes (n=58) and Gorilla gorilla (n=76). Using separate tests for each of the extant taxa, the method of resampling was to draw one mandible and one maxilla, separately, at random and with replacement, using upper and lower M2 crown areas as the metrics (as these are both represented in the relevant fossil specimens). The ratio of the LD 350-‐1 M2 area to the BOU-‐VP-‐12/130 M2 area (.647) was extremely rare in the resampled distributions (lower values were seen in only 4 of 1000 in the Pan sample, and only 6 of 1000 in the Gorilla sample). They are sufficiently outside the 95% confidence interval (Figure S10a, b) that we consider it improbable that the two fossil specimens were drawn from the same species. Accommodating the two size morphs in the same lineage that was ancestral to Homo can only reasonably be accomplished by positing large alternating shifts in mean postcanine tooth size between 2.8 and 2.3 Ma (see main text). 2. Australopithecus sediba Australopithecus sediba (Malapa cave system, Guateng Province, South Africa) is represented by two partial skeletons (one, the juvenile MH 1, with an associated cranium and mandible, the other, the adult MH 2, with a partial mandible) plus at least one isolated postcranial bone (30, 35). Dated to ~1.98 Ma, these fossils are ~.75-‐.80 Ma younger than LD 350-‐1. Berger and colleagues argued that A. sediba makes a morphologically appropriate proximate ancestor for the Homo lineage. Compared to LD 350-‐1, the A. sediba mandible, while small and lightly built (due in part to the juvenile status of MH 1 and the purported adult-‐
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female status of MH 2), is Australopithecus-‐like in its square or distally tapered lower molar crowns, deep mandibular corpus anteriorly (MH 1), and laterally (MH 1) or anteriorly oriented (MH 2) mental foramen. In addition, in facial and frontal morphology (MH 1), it strongly resembles A. africanus (34), and is potentially further tied to this species phylogenetically by a narrow range of nonmetric dental traits (36; but see 37, 38). If a unique phylogenetic link between A. sediba and A. africanus is substantiated then a direct ancestor-‐descendant relationship between A. sediba and Homo would be unlikely, as comprehensive phylogenetic analyses of craniodental characters consistently find A. africanus to be rooted basal to a strongly supported “robust” australopith-‐Homo clade (e.g., 11, 27, 39, 40). LD 350-‐1 suggests that more derived Homo-‐like mandibular and dental morphology than that of A. sediba had already evolved by 2.75-‐2.80 Ma. 3. Kenyanthropus platyops The type specimen of Kenyanthropus platyops is KNM-‐WT 40000, a crushed but fairly complete cranium, discovered in 1999 in sub-‐Tulu Bor Tuff sediments in the Kataboi member of the Nachukui Formation, Lomweki, West Turkana (41). It dates to approximately 3.5 Ma, ~0.70 Ma older than the Ledi mandible. Although it is falls within the middle of the A. afarensis temporal range, KNM-‐WT 40000 possesses mid-‐facial morphology that distinguishes it from the relatively primitive pattern seen in the Hadar sample of this species. This pattern includes reduced subnasal prognathism, a transversely flat subnasal plane, and anteriorly positioned roots of the maxillary zygomatic processes (41, 42). Leakey et al. (41) suggested broad similarities in these mid-‐facial characters to those of KNM-‐ER 1470 (Homo rudolfensis, approximately 1.9 Ma) and hypothesized a phylogenetic link. If substantiated, this would extend the ancestry of the Homo lineage into the middle Pliocene. But in Strait and Grine’s (27) analysis of early hominin phylogeny, none of the most parsimonious cladograms found Kenyanthropus to be a sister taxon to H. rudolfensis. Although the position of Kenyanthropus was unstable, it was either a sister to “robust” australopiths (=Paranthropus) or to the Homo + Paranthropus clade, and H. habilis and H. rudolfensis were always part of a consistently monophyletic Homo clade. A mandible from the Lomekwi Member of the Nachukui Formation potentially bears on the status of LD 350-‐1: KNM-‐WT 8556, a right mandible with P3-‐M1 and isolated LP3, RM2, and RM3, ~3.3 Ma (22). Leakey et al. (41) discussed this specimen but did not assign it to Kenyanthropus. Its premolar morphology falls within the A. afarensis range of variation (43), as does its mandibular corpus morphology. In comparable features, it differs from LD 350-‐1 in the same ways that Hadar A. afarensis mandibles do. The specimen has relatively enlarged P4 and M3, inconsistent with the morphology of LD 350-‐1 (the latter especially). Leakey et al. (41) discuss some ways in which the specimen differs from A. afarensis, but these have no bearing on the Ledi jaw.
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Supplementary Figures
Figure S1. Dimensions of lower fourth premolar crowns. Fig. S1 Legend. Bivariate plot of P4 crown dimensions (mm), mesiodistal (MD) length on y-‐axis, buccolingual (BL) breadth on x-‐axis. Closed circles=A. afarensis (n=21); open circles=A. africanus (n=20); crosses=A. boisei (n=9); x=A. aethiopicus (n=5); H=non-‐H. erectus early Homo (n=7); E=H. erectus (n=2); asterisk=LD 350-‐1. The convex hulls of the A. afarensis, A. africanus and A. boisei clusters are shown in red, blue, and green, respectively. The LD 350-‐1 P4 is equivalent in size to smaller A. afarensis teeth, but it is shorter mesiodistally than any known A. africanus counterpart. Authors’ data for A. africanus supplemented by (44).
8
10
12
14
16
18P4
MD
H
H
H
E
H
H
E
H
H
10 11 12 13 14 15 16P4 BL
5
Fig. S2. Dimensions of lower second molar crowns Fig. S2 Legend. Bivariate plot of M2 crown dimensions (mm), mesiodistal (MD) length on y-‐axis, buccolingual (BL) breadth on x-‐axis. Closed circles=A. afarensis (n=26); open circles=A. africanus (n=36); crosses=A. boisei (n=8); x=A. aethiopicus (n=1); H=non-‐H. erectus early Homo (n=9); E=H. erectus (n=4); asterisk=LD 350-‐1. The convex hulls of the A. afarensis, A. africanus and A. boisei clusters are shown in red, blue, and green, respectively. The LD 350-‐1 M2 is equivalent in size to smaller A. afarensis teeth, but it is much smaller, in both length and breadth, than any known A. africanus counterpart. Authors’ data for A. africanus supplemented by (44).
12
14
16
18
20
22
M2
MD
H
H
H
H
HH
EH
H
EE
E
H
11 12 13 14 15 16 17 18 19M2 BL
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Figure S3. Dimensions of lower third molar crowns Fig. S3 Legend. Bivariate plot of M3 crown dimensions (mm), mesiodistal (MD) length on y-‐axis, buccolingual (BL) breadth on x-‐axis. Closed circles=A. afarensis (n=19); open circles=A. africanus (n=20); crosses=A. boisei (n=13); x=A. aethiopicus (n=2); H=non-‐H. erectus early Homo (n=8); E= H. erectus (n=3); asterisk=LD 350-‐1. The convex hulls of the A. afarensis, A. africanus and A. boisei clusters are shown in red, blue, and green, respectively. The LD 350-‐1 M3 is smaller than known A. afarensis or A. africanus counterparts, especially in length. Authors’ data for A. africanus supplemented by (44).
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14
16
18
20
22M
3 M
D
H
HHH
H
HHH
E
E
H
E
11 12 13 14 15 16 17 18 19 20M3 BL
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Fig. S4. Quintile plots of lower first molar length.
Fig. S4 Legend. Estimated M1 mesiodistal length in LD 350-‐1 (see Supplementary Table 1) compared with distributions for A. afarensis (Hadar only) and A. africanus (Sterkfonetein and Makapansgat). Only 3/26 A. afarensis teeth and 1/32 A. africanus teeth are shorter than the LD 350-‐1 M1. Authors’ data for A. africanus supplemented by (44).
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11
12
13
14
15
16
M/1
MD
afarensis africanus LD 350-1Taxon
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Fig. S5: Comparison of mandibles of A. afarensis and LD 350-‐1
Fig. S5 Legend: Comparison of mandibular morphology of A. afarensis (A, A.L. 822-‐1) and LD 350-‐1 (B). In A. afarensis the mental foramen (red arrow) opens anterosuperiorly at the inferior edge of the lateral corpus hollow (delimited by dashed yellow line). In LD 350-‐1, the hollow is absent, and the vertical contour through the foramen is slightly convex. The mental foramen opens directly posteriorly into a short groove on the corpus. In the A. afarensis jaw the anterior margin of the ramus arises from the corpus opposite M2, whereas in LD 350-‐1 it arises opposite M3. Note also the posterior shallowing of the corpus in A. afarensis vs. the uniform corpus height in LD 350-‐1. Both images oriented on the alveolar plane and reproduced at equal P3 -‐ M2 lengths.
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Fig. S6. Anterior vs. posterior mandibular corpus height
Fig. S6 Legend. Bivariate plot expressing the relationship between mandibular corpus height anteriorly (at P3) and posteriorly (at M2). A=A. afarensis, n=12; F=A. africanus, n=3, including the young adult Sts 52b; S=A. sediba, n=1; H=early Homo. Red asterisk=LD 350-‐1. Red trend line indicates equal heights at P3 and M2. Other Homo specimens that show similar posterior and anterior corpus heights are KNM-‐BK 67 (H. erectus), KNM-‐BK 8518 (H. erectus) (15, 16), and the Sangiran H. erectus mandibular sample studied by Kaifu et al. (45). Whereas some Homo mandibles show a taller corpus anteriorly (in addition to those plotted here, this includes KNM-‐ER 60000 and SK 45), no Australopithecus mandible in our sample shows the nearly equal anterior and posterior corpus heights of the majority of early Homo mandibles and LD 350-‐1. Data for KNM-‐ER 3734, KNM-‐ER 1501, and OH 37 courtesy of F. Spoor.
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Fig. S7. Position of the anterior margin of the ramus Fig. S7 Legend. Distribution of the origin of the anterior root of the mandible’s ascending ramus among early hominins. This feature is defined as the point, in relation to the tooth row, at which the anterior margin of the ramus becomes independent of the corpus, as seen in lateral view. Blue=Australopithecus; Red=early Homo LD 350-‐1 falls in the “mid-‐M3” category (see Table S6).
0
1
2
3
4
5
6
7
8
9
mesial m2 mid m2 distal m2 m2/m3 mesial m3 mid m3 distal M3
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Fig. S8: Comparison of occlusal and basal contours of lower molar crowns Fig. S8 Legend. Relationship between the occlusal and basal crown contours of lower second molars of approximately equal occlusal wear. LD 350-‐1 (right), A. afarensis (A.L. 400-‐1a, center), and A. africanus (Stw 404, left). The buccal side is to the left in LD 350-‐1 but to the right in A.L. 400-‐1 and Stw 404. The gap between the red contour lines on the buccal side of each M2 reflects the projected horizontal distance between the occlusal and basal margins of the crown, which is large in the australopiths but small in LD 350-‐1 and early Homo. The large distances in the australopith molars reflect their characteristic bulging crown profiles. The photos were taken with the M2 occlusal surfaces parallel to the focal plane, resulting in slightly different inclinations of the M3 crowns. Equivalent differences in crown contour apply to these latter teeth, however. Note also the mesially tapered M2 and M3 crowns in LD 350-‐1, which contrasts with the distally tapered crowns in the two australopith jaws (see Table S7).
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Fig. S9: Mirror image reconstruction of LD 350-‐1. Fig. S9 Legend. Mirror image reconstruction of the LD 350-‐1 mandible from a surface laser scan of a cast. The midsagittal plane is preserved along anteroposterior sections through the corpus at positions indicated by the three yellow circles. Scale bar = 1 cm.
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Fig. S10b
Fig. S10 Legend. Distributions of resampled mandibular M2 values relative to maxillary M2 values for Pan troglodytes (Fig. S10a) and Gorilla gorilla (Fig. S10b). The ratio of the LD 350-‐1 M2 to the Australopithecus garhi (BOU-VP 12/130) M2, at .647, is larger than only 4 of 1000 Pan values and only 6 of 1000 Gorilla values.
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Supplementary Tables Table S1: Dental dimensions of LD 350-‐1
P3 P4 M1 M2 M3
Mesiodistal
Length
x 8.3
(+0.4)
(12.2) 12.8 (+0.4)
12.8 (+0.2)
Buccolingual
Breadth (midcrown)
x 10.5 x 12.5 12.2
All dimensions recorded in mm to nearest 0.1 mm. Figures in parentheses compensate for interproximal wear and should be added to the measured mesiodistal length. For estimated M1 length: the mesiodistal distance to the projected center of crown at the P4 interproximal facet is 11.8 mm. The distal wear facet on P4 is flat, not concave, so enamel loss mesially was conservatively estimated as 0.1 mm. Estimated loss of distal face enamel due to interproximal wear is 0.3 mm. Combined enamel loss is estimated at 0.4 mm, yielding a length estimate of 12.2 mm.
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Table S2: Mandibular dimensions of LD 350-‐1
Minimum Corpus Height
I1 x
I1/I2 x
I2/C x
C x
C/P3 x
P3 (31.6)
P3/P4 (31.5)
P4 x
P4/M1 x
M1 (31.7)
M1/M2 31.3
M2 (30.0)
M2/M3 29.7
M3 29.2
Minimum Corpus Breadth
P4/M1 18.0
M1 (19.3)
M1/M2 20.3
M2 20.7
M2/M3 20.7
Mental foramen position
Inferior margin to basal margin 14.8
Inferior margin to alveolar margin 16.5
P3-‐M3 tooth row length 55.0 All dimensions recorded in mm to nearest 0.1 mm. Values in parentheses are estimates (±1.0 mm). x = No measurement possible.
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Table S3: Comparison of LD 350-‐1 and A. afarensis dental and mandibular metrics
Corpus Height at M1 (mm)
Corpus Breadth at M1 (mm)
M2 MD*BL
(mm2)
M2 MD/M3 MD
P3-‐M3 tooth row length (mm)
LD 350-‐1 (31.7) (19.3) 165 1.02 55
A.L. 266-‐1 31.5 21.7 182 .82 60
A.L. 288-‐1 30.0 17.1 161 .93 (54)
A.L. 333w-‐60 38.4 23.6 212 1.02 62
A.L. 400-‐1a 35.4 18.7 219 .98 61
A.L. 417-‐1a, b 36.0 18.0 173 .86 56
A.L. 822-‐1 35.4 18.0 186 .97 59
A.L. 1045-‐1 33.9 20.4 185 .90 55
A.L. 1496-‐1 37.2 24.6 222 .84 63
Hadar mean 34.2±4.2 (21)
19.9±2.4 (23)
192±30 (27)
.93±.07 (16)
58.1±3.6 (8)
Mandibular and dental dimensions of LD 350-‐1 compared to those of Hadar Australopithecus afarensis specimens for which all five can be measured, plus the Hadar mean values (with standard deviation and sample size) for each metric. Tooth row lengths do not correct for interproximal wear but in no case was this judged to be extreme. For A.L. 288-‐1, right tooth row length is a minimum due to maleruption of the M2 relative to the postcanine axis. MD=mesiodistal length; BL=buccolingual breadth.
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Table S4: Lower molar cusp proportions in early hominins
LD
350-‐1 A. afarensis A. africanus A. robustus A. boisei early Homo
M2 n=10
n=14
n=16 n=9 n=9
Metaconid 0.204 0.226±0.22 0.227±.017 0.217±.017 0.219±.020 0.216±.015
Protoconid 0.260 0.263±.018 0.248±.023 0.227±.017 0.221±.017 0.243±.023
Hypoconid 0.232 0.197±.016 0.196±.017 0.203±.012 0.185±.011 0.211±.011
Entoconid 0.134 0.161±.023 0.173±.026 0.194±.025 0.224±.019 0.164±.020
Hypoconulid 0.170 0.153±.026 0.154±.012 0.159±.021 0.152±.026 0.167±.020
M3 n=8 n=16 n=20 n=8 n=12
Metaconid 0.189 0.228±.031 0.223±.024 0.223±.021 0.218±.018 0.230±.022
Protoconid 0.252 0.258±.018 0.247±.036 0.227±.016 0.211±.018 0.233±.029
Hypoconid 0.234 0.166±.021 0.183±.024 0.182±.021 0.150±.015 0.165±.016
Entoconid 0.109 0.170±.019 0.187±.033 0.201±.020 0.240±.035 0.178±.032
Hypoconulid 0.103 0.179±.031 0.160±.025 0.168±.025 0.181±.031 0.194±.036
C6 0.115 0.080±.043 0.082±.031 0.116±.034 0.146±.023 0.078±.023 Comparative data from Suwa et al. (8). The early Homo sample includes a mixture of south and east African specimens usually attributed to early Homo and H. erectus. Values represent proportions (± 1 standard deviation) of measured crown area of the occlusal surface occupied by each cusp. Crown areas measured from scaled occlusal photographs. The values do not sum to 1.0 in cases where minor cusp (C6, C7) areas are not provided.
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Table S5: Mandibular corpus depth proportions in early hominins Taxon Specimen @ P3 @ M2 Index
LD 350-‐1 31.6 30 1.05 A. afarensis A.L. 266-‐1 31 27.6 1.12 A.L. 288-‐1i 31 27.6 1.12 A.L. 315-‐22 32 28 1.14 A.L. 330-‐5 32 28.3 1.13
A.L. 333w-‐32+60 42.6 35.4 1.20
A.L. 417-‐1a 39 32.8 1.19 A.L. 437-‐2 44 37 1.19 A.L. 438-‐1 41 37.1 1.11 A.L. 444-‐2 44.5 37.6 1.18 A.L. 620-‐1 40 34.5 1.16 MAK-‐VP 1/12 33.4 29.6 1.13
Mean (n=10) 37.3 32.3 1.15±0.03 Homo KNM-‐ER 730 31.1 31.1 1.00
KNM-‐ER 992-‐r 32.5 32.3 1.01 KNM-‐ER 1501 27.7 26.3 1.05 KNM-‐ER 3734 35 27.5 1.27 OH 13-‐r 24.1 24.1 1.00 OH 22 27 27.5 0.98 OH 37 29.2 30.8 0.95 UR 501 36 32 1.13
Mean (n=8) 30.3 29.2 1.05±0.10
A. africanus Stw 404 28.9 24.6 1.17 Sts 52b 31.6 28.4 1.11 MLD 40 38.1 34.9 1.09
Mean (n=3) 32.9 29.3 1.13±0.04
A. sediba MH 2 31.1 27 1.15 Comparison of corpus height (defined as perpendicular corpus height; as in 46) dimensions at P3 andM2 in early hominin mandibles. The index is height at P3 divided by height at M2. Where both sides are present, the average was used. Where one side was better preserved than the other, the side used is noted in the specimen column. Sts 52b is not a full adult (M2s and canines erupted), but additional growth would not have altered the height proportions. MAK-‐VP 1/12 data from 47. Note that whereas two early Homo mandibles resemble Australopithecus in a notably deeper anterior corpus, no Australopithecus specimen has the derived subequal anterior and posterior corpus heights of early Homo and LD 350-‐1. The early Homo sample includes a mixture of specimens usually attributed to early Homo and H. erectus. See Figure S6 legend for additional information.
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Table S6: Position of the anterior ramus margin of the mandible in early hominins Species Specimen Position LG 350-‐1 mid M3 A. afarensis A.L. 128-‐23 mesial M2 A.L. 198-‐22 M2/M3 A.L. 207-‐13 mid M2 A.L. 225-‐8 distal M2 A.L. 266-‐1 mid M2 A.L. 315-‐22 distal M2 A.L. 330-‐5 distal M2 A.L. 411-‐1 mid M2 A.L. 417-‐1 M2/M3 A.L. 432-‐1 M2/M3 A.L. 437-‐2 mid M2 A.L. 438-‐1 mesial M2 A.L. 444-‐2 mid M2 A.L. 729-‐1 M2/M3 A.L. 822-‐1 distal M2 A.L. 1045-‐1 mid M2 A.L. 1180-‐1 M2/M3 A.L. 1496-‐1 distal M2 A. africanus MLD 18 mid M2 MLD 40 mesial M3 Sts 36 distal M2 Stw 14 distal M2 Stw 498 distal M2 A. sediba MH 2 M2/M3 Homo spp. OH 13 mesial M3 KNM-‐ER 992 mesial M3 KNM-‐ER 730 distal M3 KNM-‐ER 3734 mid M3 KNM-‐BK 67 mesial M3 KNM-‐BK 8518 mid M3 SK 45 distal M3 Zhoukoudian H. erectus
Locus H-‐1 distal M3
Locus G-‐1 mid M3 Distribution of the position of the of the anterior margin of the mandible’s ascending ramus among early hominins. The Homo spp. sample includes specimens usually attributed to H. habilis and African H. erectus. This feature is defined as the point at which the anterior ramus margin becomes independent of the corpus in relation to the tooth row, as seen in lateral view. Hadar A. afarensis mandible A.L. 198-‐1 lacks the anterior ramus margin and so is not scored here; while it does appear to have had a more posterior ramus margin than other specimens of A. afarensis, its possession of 4 molars confounds comparisons with other A. afarensis mandibles since the arrangement of the postcanine tooth row relative to osseous structures of the jaw is unaccountably affected.
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Table S7. Buccolingual crown breadths of lower molars (M2 and M3)
Taxon Specimen M2 Mesial Br M2 Distal Br M3 Mesial Br M3 Distal Br LD 350-‐1 11.8 12.4 11.5 12.2 A. afarensis A.L. 128-‐23 12.4 11.6 A.L. 145-‐35 14.3 13.3 A.L. 188-‐1 15.3 13.9 A.L. 198-‐1 12.9 11.8 12.1 11.6 A.L. 207-‐13 12.2 11.9 A.L. 266-‐1 13.8 12.5 13.2 11.87 A.L. 288-‐1i 12.1 11.3 11.8 10.6 A.L. 330-‐5 12.7 12.3 12.6 11.7 A.L. 333w-‐1a,b 12.7 12.4
A.L. 333w-‐32+60 14.8 14.1 14.4 13.1
A.L. 400-‐1a 14.5 13.3 13.6 12.1 A.L. 417-‐1a 13.3 12.5 13.1 12.2 A.L. 437-‐2 12.6 12.1 A.L. 620-‐1 15.4 15 A.L. 822-‐1 13.2 12.9 13 12.5 A.L. 966-‐1 15 14.6 A.L. 1045 -‐1 14.1 12.6 13.8 11.6 A.L. 1496-‐1 15.7 14.1 15.2 13.3 Mean 13.7 12.8 13.5 12.3 Homo spp. KNM-‐ER 992 11.8 11.4 11.6 10.7 KNM-‐ER 1802 14.0 14.1 OH 13 (R) 11.6 11.6 11.9 11.6 OH 7 12.6 12.6 OH 16 14.3 13.6 13.8 13.2 Mean 12.9 12.7 12.4 11.8 A. africanus Stw 498 16 15.8 16.6 15.8 Stw 404 13.7 13.1 14 13.5 Stw 384 16.7 15.7 16.7 15.6 Stw 14 13.6 14.1 Sts 52b 12.8 11.6 12.3 11.2 MLD 40 13.5 13.5 MLD 2 (R) 15 14.5 MLD 18 14.6 14.2 13.8 12.8 Mean 14.6 14.1 14.5 13.8 A. sediba MH 1 12.9 11.8 Buccolingual breadth measurements across the mesial cusps (protoconid-‐metaconid) and distal cusps (hypocinid-‐entoconid) of M2 and M3 measured perpendicular to the postcanine axis at the maximum breadth of each cusp pair. Australopithecus is characterized by distal cusps that are narrower than the mesial cusps (distal tapering), whereas Homo typically shows more similar mesial and distal breadths, especially on M2. LD 350-‐1 is unusual in showing a mesial taper, with wider cusps distally (Figure S8).
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