Supporting Information for “Endocast Morphology of Homo naledi from the Dinaledi Chamber, South Africa”

Ralph L. Holloway, Shawn D. Hurst, Heather M. Garvin, P. Thomas Schoenemann, William B. Vanti, Lee R. Berger, and John Hawks

What follows are our descriptions, illustrations, some basic interpretation, and a more specific discussion of the functional, comparative, and taxonomic issues surrounding these hominins. We use the neuroanatomical nomenclature from Duvernoy (19).

DH1 Occipital The DH1 occipital fragment (Figs 1, S2) measures ca 105 mm in width between left temporo- occipital incisure and right sigmoid sinus. It is 61 mm in height on the left side, and 47 mm on the right side. The fragment covers the entire left and mostly complete right occipital lobes. The lobes are strongly asymmetrical, with the left clearly larger than the right, and more posteriorly protruding. There are faint traces of a lateral remnant of the lunate on the left side, and a dorsal bounding lunate as well (#4 and #6 in Fig 1). The right side shows a very small groove at the end of the lateral sinus, which could be a remnant of the . The major flow from the longitudinal sinus is to the right. Small portions of both cerebellar lobes, roughly 15 mm in height are present. There is a suggestion of a great cerebellar sulcus on the right side. The width from the left lateral lunate impression to the midline is 43mm. The distance from left occipital pole (the most posteriorly projecting point, based on our best estimate of the proper orientation) to the mid-sagittal plane is 30 mm. The distance from the left occipital pole to the left lateral lunate is 29 mm. The distance from the left occipital pole to the dorsal lunate is 19 mm. Given endocranial volume (ECV) estimates of 500 ml+, these distances are significantly less than found in a large sample of chimpanzee (P. troglodytes) hemispheres (29, 30; see Table S1). The maximum width between sigmoid sinuses is 90 mm. For comparison, the same distance on STS 19 (A. africanus) is 81 mm.

These measurements and morphological features suggest that Homo naledi retained a lunate sulcus that was considerably smaller in extent than in chimpanzees, and that the dorsal remnant of the lunate is significantly reduced comparatively. The degree of asymmetry is pronounced on the left side, which in modern Homo sapiens is suggestive of right-handedness (53). Thus, while H. naledi retains some primitive retention of the pongid pattern of a lateral and anteriorly placed lunate sulcus, it nevertheless shows suggestions of the derived pattern of occipital lobe neural organization seen in modern Homo.

DH1 Calotte The DH1 calotte fragment (Fig S2) measures 107 mm in length by 92 mm in width, representing portions of left and right frontal and parietal lobes, but missing prefrontal portions as well as temporal, occipital and cerebellar lobes.

www.pnas.org/cgi/doi/10.1073/pnas.1720842115 While this fragment does not provide much convolutional detail, its size and relative completeness is extremely valuable for estimating ECV.

DH2 When placed in approximate anatomical position, the DH2 fragment (Figs S3, S4) measures approximately 111 mm in length by 88 mm in width, representing portions of the left and right frontal and parietal lobes, as well as a small portion of the right temporal and occipital lobe.

This fragment preserves the superior sagittal sinus as well as the anterior and posterior branches of the middle meningeal. A coronal suture is present. The curvature map (Fig S4) suggests possible intraparietal, superior frontal, and middle frontal sulci on the right side.

DH3 The DH3 calvaria (Figs 2, 3, S7, S9) preserves an almost complete left hemisphere, missing most of the orbital surface except in the third inferior convolution, the temporal pole, posterior parietal and occipital lobes, and the posterior part of the cerebellum. The fragment measures roughly 104 mm in length and 87 mm in height.

This fragment presents an unusual degree of cortical morphology, which is essential in providing information relevant to the question of the inclusion of these fragments within the genus Homo, irrespective of its small cranial capacity. None of the australopithecine endocasts, including the recently described A. sediba specimen (14) have as much detailed cortical morphology impressed on the internal surface of the cranial fragments as does DH3. While there are three A. africanus specimens that provide cortical morphology (Taung, STS 60, and Type 2) the interpretations are controversial given damage to the natural endocasts, as evident in the Taung specimen where flakes of the frontal, parietal and are missing, as well as the temporal pole (29). No comparison is possible with extant endocasts of A. afarensis, which lack detail in this region.

It has long been known that the inferior frontal and lateral orbital regions seen in are quite different from those seen in , based on both morphology (17, 18) and cytology (50-52). In the ancestral condition the lateral fissure opens anteriorly, exposing the anterior area of the insula, with the fronto- present anterior and medial to this and marking the posterior orbital boundary of . In Homo sapiens, the frontal lobe has expanded posteriorly and ventrally, connecting with the lateral fissure, causing the anterior area of the insula to be buried, and creating the frontal opercula (17, 18). The vertical and horizontal rami of the lateral fissure are the external homologue of superior parts of the fronto- orbital while the basal segment of the lateral fissure is the external homologue of the inferior part; the deep anterior limiting sulcus of the insula is the internal homologue (Fig 3, S6-7).

The strong presence of a fronto-orbital sulcus in the MH1 and the Type 2 (A. africanus) specimens, and the suggestion that it is present in the STS 60 and Taung (also A. africanus) specimens, shows that H. naledi is more similar to modern Homo than to Australopithecus in terms of frontal cortex morphology, despite its similarity to Australopithecus in brain size. Thickening of the orbital surface just anterior of the fronto-orbital sulcus in MH1 suggests it may represent an intermediate condition between other australopithecines and later Homo (14, 23). In DH3, a vertical ramus of the lateral fissure as well as a horizontal branch off this (Figs 3, S5, S7, S9) permits a clear identification of a particularly thickened orbital (pars orbitalis, associated with 47) as well as the frontal operculum (pars triangularis, associated with Brodmann area 45) and fronto-parietal operculum (pars opercularis, associated with Brodmann area 44). These last two opercula comprise Broca’s language area. Upon first inspection, H. naledi appears to have both a fronto-orbital sulcus and a vertical ramus of the lateral fissure with a horizontal branch. This is impossible, as they are ancestral and derived forms of the same feature. Further inspection shows the ‘fronto- orbital sulcus’ in H. naledi is not a single sulcus but two sulci separated by a medial gap. The superior one is the (Fig S5), while the ventral one is the lateral orbital sulcus (Figs S7-9).

The vertical ramus of the lateral fissure and its horizontal branch in DH3 display a Y-shaped pattern of sulcal separation, found in between 1/4 to 1/3 of modern hemispheres (17, 24). The inferior portion of the inferior third convolution suggests a pronounced pars orbitalis, while the pars triangularis is slight. Falk (21) states she recognizes a similar condition of the pars triangularis in the endocast of KNM-ER 1470 (Homo rudolfensis). This is not obvious on our copy of that endocast but would be consistent with DH3. The earliest example of human sulcal morphology we have seen in this region is the endocast of the Homo erectus specimen Trinil 2 (3, 4). Both the KNM-ER 1470 and Trinil 2 endocasts are larger than DH3, making this the smallest hominin where this modern morphology is clearly seen. Although the endocast of LB1 (H. floresiensis) is smaller still, the poor quality of the internal table of bone prevents clear identifications of sulcal morphology in the inferior frontal convolution, or parietal and temporal lobes. There appears to be no trace of a fronto-orbital sulcus however, which suggests its frontal morphology could be derived. The claim of a posteriorly positioned lunate sulcus in LB1 (54) appears reasonable. The frontal poles are associated with Brodmann area 10 and have important pre-planning behavioral functions. Similar to LB1, H. naledi’s left frontal pole suggests a somewhat larger lateral width. Evidence for these traits is clear in H. naledi because of the absence of post-depositional distortion and damage in this region of DH3.

DH4 DH4 (Figs 4, S10) is a fragment of a right occipital, parietal, temporal, and cerebellar lobe measuring ca 92 mm posterior to anterior, and ca 67 mm in height, showing considerable detail. While there appears to be both a transverse and inferior occipital sulcus, there is no obvious lunate sulcus.

DH5 The DH5 (Fig S14) fragment is ca 63 mm wide with a maximum height of 41 mm and comprises a portion of left temporal and cerebellar lobes.

U.W.101-200 The small fragment U.W.101-200 (Fig S12) is from a portion of the left occipital, showing a decussation of the longitudinal sulcus before reaching the cerebellar lobes. If this is correct, the asymmetry between degrees of posterior projection for the left and right occipital lobes is as pronounced as in DH1. Landmark #4 (Fig S12) is very suggestive of a dorsal portion of a possible lunate sulcus.

U.W.101-770 The small occipital fragment, U.W.101-770 (Fig S11) is from the right side, 38 mm wide, and 44 mm in height. The transverse sinus is 7.5 mm wide. Interestingly the sulcal details are pronounced on this small fragment, showing a great cerebellar sulcus, and an occipital lobe with unusual details, although not enough exist to suggest whether a lunate sulcus was present.

e, which was then made which made e, wasthen

analyses. Left analyses.(A), lateral Left posterior

Cranial regions represented by the seven specimens used in endocranial in used by seven the regions specimens the Cranial represented

.

S1

first aligning the 3D models of the specimens based on anatomical features to create composit create a to features based specimens 3D anatomical on models the of the aligning first variation, anatomical of of individual purple visualization to Due the interest. allow green specimen to translucent are approximate. alignments

by number. specimens Images specimen by (D) created the of views superior individual (purple) and (C), lateral right (B), Figure Figure

Figure S2. Antero-superior oblique view of 3D model of the positive endocranial surface of the DH1 calotte with oblique lighting applied and features labelled. 1-middle precentral sulcus, 2superior precentral sulcus, 3-coronal suture remnant, 4-sagittal suture, 5-middle meningeal, 6possible , 7-posterior branch of middle meningeal.

Figure S3. Lateral oblique view of 3D model of the positive endocranial surface of the DH2 with oblique lighting. 1- superior sagittal sinus, 2- possible , 3- posterior branch of middle meningeal, 4- secondary posterior branch of the middle meningeal, 5- coronal suture, 6- possible , 7- possible middle frontal sulcus.

Figure S4. Curvature map of the superior view of DH2 3D model. Blue coloration represents convex areas, while red coloration represents concave areas (depressions).

Figure S5. Curvature map of lateral view of DH3 3D model, highlighting features identified in Fig 2. Blue coloration represents convex areas, while red coloration represents concave areas (depressions).

Figure S6. Lateral view of the during the 8th month of gestational development, modified from (55). In humans the sulcus homologous to the fronto-orbital sulcus in apes (dark red) originates in a similar position to the one, but during the 7th month of gestation it begins to migrate posteriorly to connect with the anterior insula (purple) reaching its final position shortly after birth (17, 18, 55). Superiorly it operculates to become a ramus of the lateral fissure, often with an accompanying ramus or branch. Inferiorly, it operculates and closes off the anterior insula; the sulcus homologous to the fronto-orbital is here identifiable internally as the deep anterior limiting sulcus of the insula and externally as the basal segment of the lateral fissure.

Figure S7. Evolution of the lateral orbital . (A) P. troglodytes (ISIS 6167) brain “Bria” (27). (B) H. sapiens 152-subject averaged brain. (C) A. sediba MH1 endocast. (D) H. naledi DH3 endocast. See Materials and Methods for provenance of these models. In the ancestral condition seen in (A) the anterior area of the deep insula (purple) is exposed. The fronto-orbital sulcus with a horizontal branch (dark red) lies directly anterior and medial to the insula. In H. sapiens (B), the frontal lobe has expanded posteriorly and ventrally (see Figs 3, S6), causing the anterior insula to be covered over, similarly to the posterior insula. Here the vertical ramus of the lateral fissure with its horizontal branch (dark red) is the external homologue of the superior part of the fronto-orbital sulcus, while the basal segment of the lateral fissure is the external homologue of the inferior part. The buried anterior limiting sulcus of the insula (see Figure S6) is the internal homologue of the inferior fronto-orbital sulcus. In A. sediba (C) the fronto-orbital sulcus’ posterior positioning as well as thickening of the orbital surface just anterior to it suggests an intermediate condition between other australopithecines and later Homo (14, 23); in H. naledi (D) the presence of a vertical ramus of the lateral fissure with horizontal branch, a thickened orbital area immediately anterior and ventral to this, and a lateral orbital sulcus suggest frontal lobe expansion and fully derived lateral orbital gyrus morphology (23).

Figure S8. The human , from (19). LFa- lateral fissure, anterior segment, 4- lateral orbital sulcus, 4'- lateral orbital gyrus, 6- horizontal ramus of lateral fissure, 7- vertical ramus of lateral fissure, 8- pars orbitalis, 9- pars triangularis, 10- pars opercularis, 12- sulcus diagonalis.

Figure S9. The inferior frontal gyrus in (A) H. sapiens and (B) H. naledi. At first glance, H. naledi might be mistaken to have both a fronto-orbital sulcus and a vertical ramus of the lateral fissure with a horizontal branch. This is impossible, as they are ancestral and derived forms of the same feature. Further inspection shows the ‘fronto-orbital sulcus’ in H. naledi is not a single sulcus but two separate ones with a medial gap between them (seen here in B). The upper sulcus is the inferior frontal, while the lower sulcus is the lateral orbital. Compare to Fig S8.

Figure S10. Curvature map of posterior oblique view of DH4 3D model, highlighting features identified in Fig 4. Blue coloration represents convex areas, while red coloration represents concave areas (depressions).

Figure S11. Posterior view of 3D model of the positive endocranial surface of the U.W.101- 770 with oblique lighting and features labelled. 1-edge of longitudinal sinus, 2-transverse sinus, 3-cerebellar lobe, 4-horizontal cerebellar sulcus, 5-occipital lobe.

Figure S12. Posterior view of 3D model of the positive endocranial surface of the U.W.101- 200 with oblique lighting and features labelled. 1-probable lunate sulcus, 2-, 3-left occipital lobe, 4-inferior occipital sulcus, 5-longitudinal sulcus, 6-right occipital lobe.

Figure S13. Endocranial volume reconstructions using 3D prints of the DH3/DH4 (A) and DH1/DH2 (B) fragments and plasticene. Only the basal portions required reconstruction. The respective ECV’s were 460 ml (originally 465 cc) and 555 ml (originally 560 ml). See (5) for discussion of the original reconstructions.

Figure S14. Lateral view of 3D model of the positive endocranial surface of the DH5 with oblique lighting and features labelled. 1-posterior branch of middle meningeal, 2- temporooccipital incisure, 3-middle temporal sinus, 4-lateral fissure, 5-sigmoid sulcus, 6-great cerebellar sulcus.

Tables

Pan troglodytes N r BW Ave SD

OP-DL 76 0.633 P<0.001 33.6 mm 4.3 mm

OP-LL 75 0.467 P<0.001 39.6 mm 4.5 mm

Table S1. Statistics for chimpanzee measurements correlated with brain weight. OP-DL: occipital pole to dorsal lunate sulcus. BW: brain weight. OP-LL: occipital pole to most lateral lunate sulcus. Given the chimpanzee model and DH1’s estimated brain size, the OP-DL expected distance for DH1 is 66 mm; the actual distance is 19 mm. The OP-LL expected distance is 65 mm; the actual distance is 29 mm.