Despite uncontested evidence for fossils belonging to the early hominin genus Australopithecus in East Africa from at least 4.2 million years ago (Ma), and from Chad by 3.5 Ma, thus far there has been no convincing evidence of Australopithecus, Paranthropus or early Homo from the western (Albertine) branch of the Rift Valley. Here we report the discovery of an isolated upper molar (#Ish25) from the Western Rift Valley site of Ishango in Central Africa in a derived context, overlying beds dated to between ca. 2.6 to 2.0 Ma. We used µCT imaging to compare its external and internal macro-morphology to upper molars of australopiths, and fossil and recent Homo. We show that the size and shape of the enamel-dentine junction (EDJ) surface discriminate between Plio-Pleistocene and post-Lower Pleistocene hominins, and that the Ishango molar clusters with australopiths and early Homo from East and southern Africa. A reassessment of the archaeological context of the specimen is consistent with the morphological evidence and suggest that early hominins were occupying this region by at least 2 Ma.
Citation: Crevecoeur I, Skinner MM, Bailey SE, Gunz P, Bortoluzzi S, Brooks AS, et al. (2014) First Early Hominin from Central Africa (Ishango, Democratic Republic of Congo). PLoS ONE 9(1): e84652. doi:10.1371/journal.pone.0084652
Editor: Karen Rosenberg, University of Delaware, United States of America
Received: July 6, 2013; Accepted: November 17, 2013; Published: January 10, 2014
Copyright: © 2014 Crevecoeur et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Funding: Support was provided by the Brussels Institute for Research and Innovation (IRSIB, program Prospective Research for Brussels 2007–2009; PRFB 2006/CM/IV/52; http://www.innoviris.be/site/), the Franco-American Commission for Educational Exchange (Fulbright Foreign Scholarship 2010; http://www.fulbright-france.org/gene/main.php), The Centre national de la recherche scientifique (CNRS; http://www.cnrs.fr/), the Programma Vigoni (bilateral exchange program between Italy and Germany) and the Max Planck Society (http://www.mpg.de/). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.
Competing interests: The authors have declared that no competing interests exist.
The discovery of Australopithecus bahrelghazali  in Chad was significant because it extended the known range of this genus to the west of the East African Rift, where the earliest australopiths are documented to at least 4.2 Ma ago . Thereafter, for most of the Plio-Pleistocene, fossil evidence of at least one species of hominin, and at times several hominin species, is found at sites in East and southern Africa – (Figure 1). There has been extensive debate about the role played by environmental factors in the regional and temporal distributions of early hominin taxa –, but as yet, the Western (Albertine) Rift Valley, which today lies on the boundary between the tropical rain forest of the Congo basin and the savannas and woodlands of East Africa – has played little role in these debates. The Albertine Rift experienced several climatic changes at approximately 3 Ma, 2.6 Ma and 1.8 Ma that led to the partial replacement of flora and fauna of Congolian affinities with flora and fauna with similarities to East Africa that are adapted to more open conditions . During some of this period simple core and flake artifacts possibly associated with faunas that date to 2.4–2.0 Ma on biostratigraphic grounds suggest the presence of Plio-Pleistocene hominins in the Western Rift Valley of the Democratic Republic of Congo (DRC) (,Text S1 in File S1). Evidence from Ugandan part of the Western Rift Valley may also indicate Lower Pleistocene occupation of this region . However, the stratigraphic context of the finds from the Semliki Valley (i.e. Kanyatsi, Senga 5A) has been questioned (, Text S1 in File S1), and apart from a cemented block of cranial fragments and a worn molar in Western Uganda of Lower or possibly early Middle Pleistocene age provisionally attributed to Homo cf. erectus , , no pre-Upper Pleistocene hominin fossil evidence is known from this region.
Outlined in bold are the western and eastern branches of the African Rift. 1: Taung (South Africa); 2: Drimolen, Gladysvale, Gondolin, Kromdraai, Sterkfontein & Swartkrans (South Africa); 3: Malapa (South Africa); 4: Malema, Uraha (Malawi); 5: Olduvai (Tanzania); 6: Chemeron (Kenya); 7: West and East Turkana, Koobi Fora (Kenya); 8: Omo (Ethiopia); 9: Bouri, Hadar (Ethiopia).
This paper describes an unworn first upper molar (M1) (#Ish25) that the authors believe is the first compelling evidence of Plio-Pleistocene hominins in the Western Rift Valley in Central Africa. Macro and micro scale analyses have demonstrated the relevance of dental morphology for hominin taxonomy and phylogeny reconstruction (e.g. –). However, the ongoing debate about the taxonomy of the earliest members of the genus Homo - whether or not they should be removed from the clade – - and the growing complexity of Plio-Pleistocene hominin taxonomic diversity –, outline the challenge of identifying isolated dental remains to a specific taxon. Here we use µ-CT imaging to compare the external and internal macro-morphology of this M1 to those of a large sample of australopiths, and fossil and recent Homo. Our results suggest that this tooth, which most closely resembles Plio-Pleistocene hominins, provides new insights about the presence of early hominins in Central Africa.
The #Ish25 left M1 was found at Ishango 11 (IS-11) an archaeological site in the Semliki valley located in the DRC part of the Western Rift. This valley is best known for its Late Stone Age (LSA) artifacts and particularly for the early evidence for harpoons , but the recovery of stone tools in situ in the Semliki Formation (Late Lower to Middle Pleistocene) at Katanda 2, and possibly also in the Plio-Pleistocene Lusso Formation (first known as Kaiso beds ) at Kanyatsi 2 and Senga 5A, suggested that early hominins were present in the valley long before the Upper Pleistocene (, Text S1 in File S1).
Ishango 11 is located along the Semliki River where it flows out of Lake Rutanzige (or Lake Edward; see  p.3). The site was initially recognized and superficially explored in 1935 by Damas , but the first formal excavations were carried out by de Heinzelin in the 1950s during his geological and archaeological expeditions in the Upper Semliki region –. At Ishango, de Heinzelin excavated two perpendicular trenches as well as the area to the west of their junction (Text S2.1 and Figure S1 in File S1); the stratigraphy he established was later confirmed by the work of the Semliki Research Expedition –. Recent to Upper Pleistocene lithostratigraphic units compose a terrace complex TT (or Terrasse tuffacée) later redefined as the Ishango Gravels Formation  that truncated and overlies the Plio-Pleistocene Lusso Formation (Figure 2, Text S2.2 and Figure S2 in File S1). The latter have been dated using biochronology to between 2.6 Ma and 2.0 Ma (–, –, Text S2.2 in File S1). Towards the base of the Ishango Gravels Formation, overlying the ca. 1m thick basal gravels (G.INF), a 10–20 cm thick Niveau Fossilifère Principal (NFPr) yielded an early Late Stone Age (LSA) assemblage consisting of numerous lithic and bone artifacts as well as faunal remains (, , –, Text S2.2 in File S1) in association with more than a hundred heavily mineralized hominin remains. Radiometric dating of the LSA layer (NFPr) yielded an age between 25–19 Ka (–, , Text S2.2 in File S1), an age consistent with that suggested by characteristics of the faunal assemblage . During the initial study of the 1950s LSA hominin remains, it was assumed that all were attributed to Homo sapiens. However, the exceptionally large size of a left M1 (#Ish25) described by Twiesselmann , raised the possibility that evidence of a more primitive hominin may have been mixed in with a fossil assemblage that is otherwise similar to anatomically modern humans.
ZPEm = Post-Emersion Zone; N.TUF = Tuffaceous Levels; SD-SFM = Hardened Sand - Fine Micaceous Sand, NFPr = Principal Fossiliferous Level, G.INF = Inferior Gravels, Lusso = Lusso Beds, R = Recent, TP = Museya Gravels Formations, TT = Ishango Gravels Formation, L = Lusso Formation.
Results and Discussion
Origin of the Tooth
Although the precise location of the archeological samples and the description of their content were recorded by de Heinzelin in his notebook, there was no mention of an isolated tooth. Archival research, however, has revealed that #Ish25 was discovered the first day of de Heinzelin’s excavation, and that it came from the corner area, west of the junction of the trenches (Text S2.3 and Figures S3–S8 in File S1). This area preserved only the basal parts of the Upper Pleistocene Ishango Gravels Formation, namely levels G.INF and NFPr (, Text S2.3 in File S1). In the archives of the excavation, de Heinzelin indicated that intrusive fossils from the Lusso Formation had been reworked into the lower layers of the Ishango Gravels Formation (Figure S7 in File S1: “G.INF = Inferior gravels with few fossils, rare harpoons and reworked Kaiso fossils”). In 1955 and 1957, de Heinzelin described the G.INF layer as an unstratified mass of rolled gravels including numerous fragments of reworked fossils from the Lusso/Kaiso Formation (brown bullhead, crocodile, etc.) mixed together with fauna and artefacts accounting for the first stages of the Ishango civilization (–, Text S2.3 and Figures S2 and S7 in File S1). The same observations were made by Greenwood  and Hopwood & Misonne  for the fish and mammal assemblage at the base of the Ishango Gravels Formation. The analysis of the fauna by Peters confirmed the heterogeneity of the basal layers from the Ishango Gravels Formation . He identified reworked intrusive elements (shell fragments) in the G.INF and the NFPr deposits that originate from the older sediments. Since the presence of reworked fossils from the Lusso Formation is confirmed by archaeozoological studies in both basal layers of the Ishango Gravels Formation, this is a legitimate reason to argue that #Ish25 likely derives from the underlying Plio-Pleistocene Lusso Formation and should not be grouped with the LSA hominin fossils.
In order to test the hypothesis that #Ish25 may be a reworked element within the Ishango Gravels Formation, we used Raman spectroscopy, a non-destructive technique, to analyze and compare the diagenetic processes at work in this tooth with those seen in the three teeth from the LSA level that best represented the range of taphonomic alterations seen in fossils from this horizon (Text S3 and Figure S9 in File S1).
The Raman spectra acquired from the NFPr material show signatures consistent with dentine spectra (–, Figure 3). The three teeth show a similar diagenetic signal, with a 963.5 cm−1 peak (υ1(PO4)3−) with a mean signal-to-noise ratio (S/N) of 1250 (ranging from 967 to 1368); there is no evidence of (PO4)3− secondary features. The spectra from #Ish25 show an intense 963 cm−1 peak (mean S/N of 2152) and a 1074 cm−1 peak (υ1 (CO3)2−) with a mean S/N of 456; (PO4)3− secondary features at 430 cm−1 and 590 cm−1 (respectively υ2(PO4)3− and υ4(PO4)3−) are also present (Text S3 in File S1). The results of the Raman spectroscopy suggest that #Ish25 has a distinctive Raman spectrum compared to the three teeth from the NFPr layer. In particular, #Ish25 has a doubled intensity for the (υ1(PO4)3−) phosphate peak and a clear carbonate signal, suggesting a difference in hydroxyapatite re-crystallization and carbonate integration. This supports the hypothesis that #Ish25 has a different diagenetic history than the remains from the NFPr layer, and is consistent with it being an intrusive element within the basal section of the Upper Pleistocene terrace.
The results from the Raman spectroscopy, plus the archival and geological evidence (Texts S1–S3 in File S1), are consistent with #Ish25 being a reworked element from the Lusso Formation.
Comparative Morphometric Analyses of Ishango First Upper Molar
Upper part, from top to bottom: buccal, mesial, occlusal, lateral and lingual views. Scale bar = 1 cm. Lower part, three-dimensional model of the outer enamel surface (left) and the enamel-dentine junction (right).
The stage of root formation (scale E; ), together with the absence of interproximal wear facets, suggests that it belongs to an immature individual and that the tooth was not fully erupted. The shape of the distobuccal corner of the crown, the relative equivalence of the mesiolingual-distobuccal and mesiobuccal-distolingual axes, the slightly larger dimension of the lingual face compared to the buccal one, and the triradiate fissure pattern in the central fossa of the occlusal surface indicate that this tooth is a first upper molar –. The identification of #Ish25 as a first molar is also supported by analysis of EDJ shape (see below and Text S4.4 and Tables S5–S7 in File S1).
The outer enamel surface of #Ish25 is marked by two crests - a C-shaped anterior transverse crest that joins the mesial marginal ridge (MMR) and a notched, but uninterrupted, crista obliqua between the protocone and the metacone. A third crest, a trigonal-hypocone crest that results in a shallow groove at this location on the OES, is only visible on the EDJ surface. The mesial marginal ridge bears three tubercles at the OES that correspond with dentine horn-like projections at the EDJ . There is no metaconule (or cusp 5). A furrow-like Carabelli structure is visible on the lingual OES of #Ish25 with a corresponding depression at the EDJ.
The taxonomic implications of non-metric enamel and dentine characters have been debated , , . The tubercles on the MMR have limited significance , and the expressions of the three crests on #Ish25 have been interpreted as primitive features . The continuous crista obliqua is observed in a minority of recent modern humans at the OES (ca. 20%); it is most frequent in early Homo and it is also developed in hyper-megadont archaic hominins , . The particular C-shaped anterior transverse crest on the EDJ is found in less than 2% of modern human individuals, and it is also rare among australopiths . While the incidence of a furrow-like Carabelli structure in modern human populations varies ca. 12% to ca. 44% , its occurrence in early hominins is higher among early Homo (ca. 33%) than Australopithecus and Paranthropus (ca. 18.5%) .
The exceptional dimensions of the #Ish25 crown have been noted since its discovery , . The mesiodistal and buccolingual diameters of #Ish25 align it with australopiths rather than with Pleistocene Homo and recent modern humans (Text S4.1, Table S1 and Figure S10 in File S1). The crown base area of the #Ish25 falls at the upper end of the early Homo variation and between the means of Australopithecus and Paranthropus (Text S4.2 and Table S2 in File S1). The cusp areas of #Ish25 have the following relative size relationships: protocone >paracone>metacone>hypocone. The ratio between the size of the paracone and the metacone separates Australopithecus and early Homo from later Pleistocene Homo . In #Ish25 the paracone is 5.5% larger than the metacone, a relationship that aligns this individual with later Homo specimens (Figures S11–S12 in File S1). However, the complexity of the mesial marginal ridge morphology complicates this assessment, for it is not clear whether the diagnostic paracone/metacone relationship holds true for teeth with as many accessory cusps/cuspules as are observed in #Ish25.
Since the relative proportions of enamel and dentine have been used to assess hominid phylogeny, taxonomy and adaptation (e.g. , –), we further investigated the two- and three-dimensional dental tissue proportions of #Ish25 through micro-computed tomography. In Tables S3 and S4 (in File S1) we compare the results with the available data on hominin upper molars. With the exception of the Neanderthals (, Text S4.3 in File S1), dental tissue proportions similar to modern humans are documented back to the Middle Pleistocene –, whereas australopiths are characterized by thicker enamel –. The proportions of enamel and dentine exhibited by #Ish25 are closer to the pattern seen in early hominins than to the values seen in both Middle-to-Upper Pleistocene Homo and recent humans. In relation to its crown size, the enamel thickness of #Ish25 is comparable to that of the M1s from Sterkfontein (i.e. Sts 57) and Swartkrans (i.e. SK 832) (Figures S13–S14 in File S1).
We used geometric morphometrics to examine the shape of the #Ish25 EDJ based on landmarks and semilandmarks (, , Text S4.4 and Figure S15 in File S1). A principal component analysis of the Procrustes coordinates in both shape and form space (i.e. including also tooth size; see Text S4.4 in File S1) shows a clear separation on the first axis between the Pliocene-Lower Pleistocene hominins and the Middle Pleistocene-recent specimens (Figure 5), with #Ish25 clustering with the former group at the interface of the P. robustus and A. africanus convex hulls. A cross-validated canonical variates analysis of EDJ shape classifies #Ish25 as most similar in morphology to the early Homo comparative sample (Text S4.4 in File S1), while a nearest neighbor analysis links #Ish25 with the A. africanus specimen Sts 8 (not illustrated). A comparison of the EDJ shape of the #Ish25 with the mean shape of the post-Lower Pleistocene sample and the mean shape of the Plio-Pleistocene sample indicates that the relative size and position of the dentine horns of the four main cusps (the ridge curve) and the shape of the cervix of #Ish25 match more closely the mean of the Plio-Pleistocene sample. This pattern is even more pronounced in form space, which includes tooth size in the comparison (Figure S16 in File S1). While it is clear that the EDJ shape of the Ishango molar is consistent with it belonging to an early hominin taxon, the lack of a more comprehensive early Homo EDJ sample prevents definitive assignment to a specific taxon.
Projection of the first three principal components of the PCA of the enamel-dentine junction (EDJ) morphology. Solid lines in each convex hull represent static allometric trajectories for respective groups. Abbreviations: Sangiran specimens (S4, S7), Qafzeh specimens (Q9, Q10, Q15) and Steinheim (St).
A reassessment of the Ishango archaeological collections has highlighted the uniqueness of #Ish25, a particularly large hominin first upper molar. The combination of archival evidence about its geological context and the results of Raman spectroscopic analysis suggest that #Ish25 does not belong to the Upper Pleistocene LSA modern human assemblage. With the exception of the derived relative cusp proportions, the external and internal dental morphology of #Ish25 resembles that of australopiths or early Homo and the absolute and relative dimensions of the crown and its relatively thick enamel align it with East and southern African early hominins. Finally, in a detailed analysis of the EDJ, which discriminates between australopiths/early Homo and post-Lower Pleistocene Homo, #Ish25 clusters with the former.
The attribution of #Ish25 to an early hominin has several implications. Locally, this occurrence is consistent with archaeological evidence suggesting that early hominins were in the Semliki valley close to, if not prior to, two million years before the present. More globally, our understanding of early hominin evolution, adaptation and dispersion during the Plio-Pleistocene period is mainly based on fossil evidence from just two regions within the vast African continent, the Eastern Rift Valley from Ethiopia to Tanzania, and southern Africa. The #Ish25 first upper molar is meager, but compelling, evidence that by ca. 2 Ma early hominins had expanded their geographical range into the Western Rift valley of Central Africa, and had occupied a region whose environment has been reconstructed as a woodland to grassland ecotone adjacent to dense lowland forests , .
Overall, the evidence from Ishango provides a new perspective on hominin morphological and ecological diversity during the Plio-Pleistocene and contributes to our understanding of the patterns of dispersal and evolution of early hominins.
Materials and Methods
The upper molar #Ish25 belongs to the Ishango collection (inventory number IG 22295) housed in the department of Anthropology and Prehistory in the Royal Belgian Institute of Natural Sciences (RBINS), Brussels, Belgium.
We are grateful to the following institutions and persons that gave permission to study the comparative material. In the following cases, the institution was the legal repository for the fossil material: Archéologie andennaise, Belgium (D. Bonjean), Senckenberg Research Institute (F. Schrenk and O. Kullmer), Croatian Museum of Natural History (J. Radovčić), Ditsong National Museum of Natural History (S. Potze), Institut de Paléontologie Humaine (H. de Lumley, D. Grimaud-Hervé), Institutul de Antropologie “Francisc I. Rainer” (A. D. Soficaru), Max Planck Institute for Evolutionary Anthropology (J.-J. Hublin), Museo Nacional de Ciencias Naturales (A. Rosas), Musée d’Angoulême (J.-F. Tournepiche), Musée d’Archéologie Nationale, National Museums of Kenya (E. Mbua), Musée National de Préhistoire (J.-J. Cleyet-Merle), Rockefeller Museum, Sackler School of Medicine (Y. Rak, A. Barash, I. Hershkovitz), University of Witwatersrand (B. Zipfel), Staatliches Museum für Naturkunde (R. Ziegler), Rheinisches Landesmuseum (H. Joachim), Russian Academy of Science Archaeology Institute (T. Balueva), National Museum of Archaeology in Lisbon, Iziko South African Museum. In the case of the British Museum (N. Spencer, D. Antoine), the Department of Anthropology in the Colorado University in Boulder (D. Van Gerven), and the Royal Belgian Institute of Natural Sciences, the specimen(s) was/were donated to the institution. The specimens from the Department of Anthropology of the National Museum of Natural History (Smithsonian Institution, D. Hunt) are on loan. S. Prat and H. Roche gave access to the specimen in their care. Finally, the comparative material from the Museum für Vor- und Frühgeschichte, Staatliche Museum zu Berlin (A. Hoffmann & W. Menghin) was purchased by this institution.
We used a 785 nm (NIR) laser Raman spectrometer (Senterra, Olympus BX51, Bruker optics) for the analysis of the Ishango teeth. The spectra were acquired using a 2 mW 785 nm laser, during 3×10 s and with a 50×1000 µm spectrometer slit. Raman spectra fluorescence removal and curve-fitting techniques were applied to each of the acquired spectra to overcome the fluorescence problem when Raman spectroscopy is applied to human remains . Confocal Raman microscopy, in a slightly out of focus position, reduced the influence of the resin coating. Several spectra (∼10) were collected on the dentine surface of each tooth and the average used for comparison.
The micro-computed tomography (µ-CT) of #Ish25 was performed at the Scan Research Group Laboratory at the University of Antwerp, Belgium. The specimen was scanned with the SkyScan 1173 high energy spiral X-ray microtomograph with a tube voltage of 130 kV (61 µA current and a projection each 0.2° of rotation) and a resolution of 10 µm. In order to facilitate processing, the volume was re-sampled to a voxel size of 40 µm.
The µ-CT data set of #Ish25 can be downloaded at a resolution of 20 µm following this URL: http://africanarchaeology.naturalsciences.be/archaeological-sites/dem.-rep.-congo-zaire/Ishango/IV.%20Collections/2.%20Human%20Remains/c.%20Files%203D/teeth/ishango-25.
Threshold values between segmented tissues were determined following the half-maximum height methods – using Aviso 6.1 (www.vsg3d.com). The two-dimensional dental tissue proportions of #Ish25 were taken on the virtual mesial cross-section of the tooth following the method developed by Martin  and using ArteCore (©2004–2006 ART+COM AG). Three-dimensional data were recorded following the protocols defined by Kono , Tafforeau  and Olejniczak  using Amira 5 (©2008 Visage Imaging, Inc.). The cervical plane (to measure coronal dentine and coronal pulp) was computed following the definitions of Olejniczak , .
Regarding the comparative sample, the taxonomic attributions of Australopithecus and early Homo M1 follow Wood & Engelman , Wood , Quam et al.  and Clarke . Comparative assessment of #Ish25’s external crown dimensions and proportions was performed using classical linear measurements  and the method described by Quam et al. . The comparative data were compiled from published data and original fossils (Texts S4.1 and S4.2 in File S1). The mean and range of variation of the comparative groups are given in Table S1 (in File S1) and Table S2 (in File S1). Two-dimensional dental tissue proportion data from #Ish25 were compared to published data on M1s from australopiths, and fossil and recent Homo –, –, ,  in Table S3 (in File S1) and Figure S13 (in File S1). The recent modern human sample (RMH) was compiled by mathematically combining the sub-sample means and standard deviations using the formula of Cleuvenot & Houët . The upper molar comparative samples used in the 3D dental tissue proportions analyses come from Olejniczak et al. –, . Although several studies have emphasized comparisons of dental tissue proportions between teeth of similar positions , , we used combined samples of upper molars to maximize the comparative sample size (Table S4 in File S1). With respect to the geometric morphometric analysis, the process by which landmarks and semilandmarks – was generated and compared for each specimen is detailed in the Text S4.4 (in File S1). Landmarks were placed around the cervix of the crown and around the ridge curves that link the dentine horns of the protocone, paracone, metacone and hypocone. The comparative sample, which includes Pleistocene and recent Homo sapiens, Neandertals, Homo erectus from Indonesia, early Homo from east and southern Africa, Paranthropus robustus, and Australopithecus africanus is given in Table S5 (in File S1).
File includes supporting text, supporting figures, and supporting tables.
Text S1. Previous evidence of hominin occupation in the Western Rift Valley
Text S2. Ishango Site
Text S2.1 History of excavations
Text S2.2 Stratigraphy and Dating
Text S2.3 Origin of #Ish25 upper molar
Text S3. Raman spectroscopic analysis
Text S4. Morphometric comparison
Text S4.1 Crown dimensions
Text S4.2 Cusp area analysis
Text S4.3 Two- and three-dimensional dental tissue proportions
Text S4.4 Enamel-dentine junction (EDJ) morphology References
Figure S1. The excavation plan at Ishango 11
Figure S2. Schematized stratigraphic section of the ten first meters of Ishango N43GE trench
Figure S3. Letter from de Heinzelin to Twiesselmann dated to Sunday 23rd of April 1950. Recto
Figure S4. Letter from de Heinzelin to Twiesselmann dated to Sunday 23rd of April 1950. Verso
Figure S5. First page of the Heinzelin notebook
Figure S6. Letter from de Heinzelin to the director of the RBINS dated to the 16th of February 1951
Figure S7. First sketch of a stratigraphical section with the definition of the archaeological layers
Figure S8. First map of the Ishango excavation dated from the 5th to 9th of May 1950
Figure S9. Photographs of the teeth from the LSA human assemblage (NFPr level) that were used as comparative samples for the Raman spectroscopic analyses
Figure S10. Bivariate plot of the crown diameters of #Ish25 and the comparative sample (cf. Table S1)
Figure S11. Bivariate plot of the relative paracone area in relation to the relative metacone area. Comparative samples as in Table S2
Figure S12. Scatter plot of the first and second principal components of the PCA on relative cusp areas. Comparative samples as in Table S2
Figure S13. Adjusted Z-scores of the two-dimensional dental tissue proportions of #Ish25
Figure S14. Bivariate plot of the volume of coronal dentine (DPVOL) and the relative enamel thickness (RET3D)
Figure S15. Illustration of landmarks collected on the ridge curve, cervix curve and main dentine horns
Figure S16. Comparison of the EDJ shape of #Ish25
Table S1. Crown dimensions (mm) of #Ish25 and the comparative group means and standard deviations
Table S2. Comparison of crown and cusp areas between Ishango #Ish25 and comparative fossil groups (mm2)
Table S3. Two-dimensional dental tissue proportions of M1 #Ish25 and the first upper molar comparative samples
Table S4. Three-dimensional dental tissue proportion of M1 #Ish25 and the pooled upper molar comparative samples
Table S5. First molar sample used to analyze EDJ shape of the #Ish25 molar
Table S6. Second molar sample used to assess the classification of #Ish25 as a first molar
Table S7. Classification of the M1/M2 comparative sample using a cross-validated CVA
We are grateful to the following institutions and persons that gave permission to study the comparative material. In the following cases, the institution was the legal repository for the fossil material: Archéologie andennaise, Belgium (D. Bonjean), Senckenberg Research Institute (F. Schrenk and O. Kullmer), Croatian Museum of Natural History (J. Radovčić), Ditsong National Museum of Natural History (S. Potze), Institut de Paléontologie Humaine (H. de Lumley, D. Grimaud-Hervé), Institutul de Antropologie “Francisc I. Rainer” (A. D. Soficaru), Max Planck Institute for Evolutionary Anthropology (J.-J. Hublin), Museo Nacional de Ciencias Naturales (A. Rosas), Musée d’Angoulême (J.-F. Tournepiche), Musée d’Archéologie Nationale, National Museums of Kenya (E. Mbua), Musée National de Préhistoire (J.-J. Cleyet-Merle), Rockefeller Museum, Sackler School of Medicine (Y. Rak, A. Barash, I. Hershkovitz), University of Witwatersrand (B. Zipfel), Staatliches Museum für Naturkunde (R. Ziegler), Rheinisches Landesmuseum (H. Joachim), Russian Academy of Science Archaeology Institute (T. Balueva), National Museum of Archaeology in Lisbon, Iziko South African Museum. In the case of the British Museum (N. Spencer, D. Antoine), the Department of Anthropology in the Colorado University in Boulder (D. Van Gerven), and the Royal Belgian Institute of Natural Sciences, the specimen(s) was/were donated to the institution. The specimens from the Department of Anthropology of the National Museum of Natural History (Smithsonian Institution, D. Hunt) are on loan. S. Prat and H. Roche gave access to the specimen in their care. Finally, the comparative material from the Museum für Vor- und Frühgeschichte, Staatliche Museum zu Berlin (A. Hoffmann & W. Menghin) was purchased by this institution. We also want to thank the European Synchrotron Radiation Facility (P. Tafforeau), as well as P. Bayle, M. Tocheri and J.-J. Hublin for their assistance and advice regarding various aspects of this study. Finally, we would like to thank the anonymous reviewers for their helpful comments on the first version of this manuscript.
Conceived and designed the experiments: IC MMS SEB PG BW. Performed the experiments: IC MMS SEB PG. Analyzed the data: IC MMS SEB PG ASB EC PS. Contributed reagents/materials/analysis tools: IC MMS SEB PG SB CB ND BM PS YV. Wrote the paper: IC MMS SEB ASB EC BW.
- 1. Brunet M, Beauvilain A, Coppens Y, Heintz E, Moutaye AHE, et al. (1995) The first australopithecine 2,500 kilometers west of the Rift Valley (Chad). Nature 378: 273–275. doi: 10.1038/378273a0
- 2. Leakey MG, Feibel CS, McDougall I, Walker A (1995) New four-million-year-old hominid species from Kanapoi and Allia Bay, Kenya. Nature 376: 565–571. doi: 10.1038/376565a0
- 3. Walker A, Leakey RE, Harris JM, Brown FH (1986) 2.5-Myr Australopithecus boisei from west of Lake Turkana, Kenya. Nature 332: 517–522. doi: 10.1038/322517a0
- 4. Kimbel WH, Walter RC, Johanson DC, Reed KE, Aronson JL, et al. (1996) Late Pliocene Homo and Oldowan Tools from the Hadar Formation (Kada Hadar Member), Ethiopia. J Hum Evol 31: 549–561. doi: 10.1006/jhev.1996.0079
- 5. Wood B (1992) Origin and evolution of the genus Homo. Nature 355: 783–790. doi: 10.1038/355783a0
- 6. Kimbel WH (2007) The Species and Diversity of Australopiths. In: Henke W, Tattersall I, editors. Handbook of Paleoanthropology. Berlin: Springer-Verlag. PP. 1539–1574.
- 7. Vrba ES (1988) Late Pliocene climatic events and hominid evolution. In: Grine FE, editor. Evolutionary history of the “robust” australopithecines. New York: Aldine de Gruyter. PP. 405–426.
- 8. deMenocal PB (1995) Plio-Pleistocene African climate and the paleoenvironment of human evolution. Science 270: 53–59. doi: 10.1126/science.270.5233.53
- 9. Stanley SM (1995) Climatic Forcing and the Origin of the Human Genus. In: National Research Council, editors. Effects of past global change on life. Washington: National Academy Press. 233–244.
- 10. Potts R (1998) Environmental Hypotheses of Hominin Evolution. Yearb Phys Anthropol 41: 93–136. doi: 10.1002/(sici)1096-8644(1998)107:27+<93::aid-ajpa5>3.0.co;2-x
- 11. Kingston JD (2007) Shifting Adaptive Landscapes: Progress and Challenges in Reconstructing Early Hominid Environments. Yearb Phys Anthropol 50: 20–58. doi: 10.1002/ajpa.20733
- 12. Boaz NT (1990) The Semliki Research Expedition: History of Investigation, Results, and Background to Interpretation. In: Boaz NT, editor. Evolution of Environments and Hominidae in the African Western Rift Valley. Martinsville: Virginia Museum of Natural History. PP. 3–14.
- 13. Pickford M, Senut B, Hadoto D (1993) Geology and Palaeobiology of the Albertine Rift Valley, Uganda-Zaire. Volume I: Geology. Orléans: C.I.F.E.G. 190 p.
- 14. Boaz NT, Bernor RL, Brooks AS, Cooke HBS, de Heinzelin J, et al. (1992) A new evaluation of the significance of the Late Neogene Lusso Beds, Upper Semliki Valley, Zaire. J Hum Evol 22: 505–517. doi: 10.1016/0047-2484(92)90083-l
- 15. Harris JWK, Williamson PG, Morris PJ, de Heinzelin J, Verniers J, et al.. (1990) Archaeology of the Lusso Beds. In: Boaz NT, editor. Evolution of Environments and Hominidae in the African Western Rift Valley. Martinsville: Virginia Museum of Natural History. 237–272.
- 16. de Heinzelin J, Verniers J (1996) Realm of the Upper Semliki (Eastern Zaire). An essay on historial geology. Tervuren: Royal Museum of Central Africa. 87 p.
- 17. Senut S, Pickford M, Ssemmanda I, Elepu D, Obwona P (1987) Découverte du premier Homininae (Homo sp.) dans le Pléistocène de Nyabusosi (Ouganda Occidental). C R Acad Sci Paris 305: 819–822.
- 18. Korenhof CAW (1960) Morphogenetical aspects of the human upper molar: a comparative study of its enamel and dentine surfaces and their relationship to the crown pattern of fossil and recent primates. Utrecht: Uitgeversmaatschappij Neerlandia. 368 p.
- 19. Martin L (1985) Significance of enamel thickness in hominoid evolution. Nature 314: 260–263. doi: 10.1038/314260a0
- 20. Wood BA, Engleman CA (1988) Analysis of the dental morphology of Plio-Pleistocene hominids. V. Maxillary postcanine tooth morphology. J Anat 161: 1–35.
- 21. Bailey S (2004) A morphometric analysis of maxillary molar crowns of Middle-Late Pleistocene hominins. J Hum Evol 47: 183–198. doi: 10.1016/j.jhevol.2004.07.001
- 22. Dean MC (2006) Tooth microstructure tracks the pace of human life-history evolution. Proc. R. Soc. B 273: 2799–2808. doi: 10.1098/rspb.2006.3583
- 23. Skinner MM, Gunz P, Wood BA, Hublin JJ (2008) Enamel-dentine junction (EDJ) morphology distinguishes the lower molars of Australopithecus africanus and Paranthropus robustus. J Hum Evol 55: 979–988. doi: 10.1016/j.jhevol.2008.08.013
- 24. Wood B, Collard M (1999) The Human Genus. Science 284: 65–71. doi: 10.1126/science.284.5411.65
- 25. Wood B (2010) Reconstruction human evolution: Achievements, challenges, and opportunities. Proc Natl Acad Sci U S A 107: 8902–8909. doi: 10.1073/pnas.1001649107
- 26. Leakey MG, Spoor F, Dean MC, Feibel CS, Anton S, et al. (2012) New fossils from Koobi Fora in northern Kenya confirm taxonomic diversity in early Homo. Nature 488: 201–204. doi: 10.1038/nature11322
- 27. Berger LR (2013) The mosaic nature of Australopithecus sediba. Science 340: 163. doi: 10.1126/science.340.6129.163
- 28. Yellen JE, Brooks AS, Cornelissen E, Mehlman MJ, Stewart K (1995) A Middle Stone Age worked bone industry from Katanda, Upper Semliki Valley, Zaire. Science 268: 553–556. doi: 10.1126/science.7725100
- 29. Fuchs V (1934) The geological work of the Cambridge expedition to the East African lakes, 1930–1931. Geological magazine 71: 97–112 72: 145–166. doi: 10.1017/s0016756800093067
- 30. Damas H (1940) Observations sur les couches fossilifères bordant la Semliki. Revue de Zoologie et de Botanique Africaines 33: 265–272.
- 31. de Heinzelin J (1957) Les fouilles d’Ishango. Bruxelles: Institut des Parcs nationaux du Congo belge. 128 p.
- 32. de Heinzelin J (1955) Le fossé tectonique sous le parallèle d’Ishango. Bruxelles: Institut des Parcs nationaux du Congo belge. 150 p.
- 33. de Heinzelin J (1961) Le Paléolithique aux abords d’Ishango. Bruxelles: Institut des Parcs nationaux du Congo et du Ruanda-Urundi. 34 p.
- 34. Brooks AS, Helgren D, Cramer JS, Franklin A, Hornyak W, et al. (1995) Dating and Context of Three Middle Stone Age Sites with Bone Points in the Upper Semliki Valley, Zaire. Science 268: 548–553. doi: 10.1126/science.7725099
- 35. Brooks AS, Smith CC (1987) Ishango revisited: new age determinations and cultural interpretations. Afr Archaeol Rev 5: 65–78. doi: 10.1007/bf01117083
- 36. Adam W (1957) Mollusques quaternaires de la région du lac Edouard. Bruxelles: Institut des Parcs nationaux du Congo belge. 172 p.
- 37. Gautier A (1970) Fossil fresh water mollusca of the Lake Albert-Lake Edward rift (Uganda). Annalen - Koninklijk Museum voor Midden-Afrika. Geologische wetenschappen 67: 5–144.
- 38. Le Personne J (1970) Revision of the fauna and the stratigraphy of the fossiliferous localities of the Lake Albert-Lake Edward rift (Congo). Annalen - Koninklijk Museum voor Midden-Afrika. Geologische wetenschappen 67: 171–207.
- 39. Van Damme D, Pickford M (1994) The Late Cenozoic freshwater molluscs of the Albertine Rift, Uganda-Zaire: Evolutionary and Palaeoecological implications. In: Senut S, Pickford M, editors. Geology and palaeobiology of the Albertine Rift Valley, Uganda-Zaire. Volume 2, Palaeobiology. Orléans: C.I.F.E.G. PP. 71–87.
- 40. Van Neer W (1994) Cenozoic fish fossils from the Albertine Rift Valley in Uganda. In: Senut S, Pickford M, editors. Geology and palaeobiology of the Albertine Rift Valley, Uganda-Zaire. Volume 2, Palaeobiology. Orléans: C.I.F.E.G. PP. 89–128.
- 41. Brown FH, McDougall I, Davies T, Maier R (1985) An Integrated Plio-Pleistocene Chronolgy for the Turkana Basin. In: Delson E, editor. Ancestors: The Hard Evidence. New York: Alan R. Liss. PP. 82–90.
- 42. Cooke HBS (1990) Suid Remains from the Upper Semliki Area, Zaire. In: Boaz NT, editor. Evolution of Environments and Hominidae in the African Western Rift Valley. Martinsville: Virginia Museum of Natural History. PP. 197–201.
- 43. Twiesselmann F (1958) Exploration du Parc National Albert. Mission J. de Heinzelin de Braucourt (1950). Les ossements humains du gîte mésolithique d’Ishango. Bruxelles: Institut des Parcs nationaux du Congo belge. 125 p.
- 44. Greenwood PH (1959) Quaternary fish-fossils. Bruxelles: Institut des Parcs nationaux du Congo belge. 120 p.
- 45. Hopwood AT, Misonne X (1959) Mammifères fossiles. Bruxelles: Institut des Parcs nationaux du Congo belge. 120 p.
- 46. Verheyen W (1959) Oiseaux fossiles. Bruxelles: Institut des Parcs nationaux du Congo belge. 120 p.
- 47. Stewart KM (1989) Fishing Sites of North and East Africa in the Late Pleistocene and Holocene. Environmental Change and Human Adaptation. Oxford: BAR international series. 273 p.
- 48. Peters J (1990) Late Pleistocene hunter-gatherers at Ishango (Eastern Zaire): The faunal evidence. Revue de Paléobiologie 9: 73–112.
- 49. Mercader J, Brooks AS (2001) Across Forests and Savannas: Later Stone Age Assemblages from Ituri and Semliki, Democratic Republic of Congo. J Anthropol Res 57: 197–217.
- 50. Brooks AS, Robertshaw P (1990) The Glacial Maximum in tropical Africa: 22 000–12 000 BP. In: Gamble C, Soffer O, editors. The World at 18 000 BP: Low Latitudes. Volume 2. London: Unwin Hyman. PP. 121–169.
- 51. Suzuki M, Kato H, Wakumoto S (1991) Vibrational Analysis by Raman Spectroscopy of the Interface Between Dental Adhesive Resin and Dentin. J Dent Res 70: 1092–1097. doi: 10.1177/00220345910700071501
- 52. Tsuda H, Ruben J, Arends J (1996) Raman spectra of human dentin mineral. Eur J Oral Sci 104: 123–131. doi: 10.1111/j.1600-0722.1996.tb00056.x
- 53. Demirjian A, Goldstein H, Tanner JM (1973) A new system of dental age assessment. Hum Biol 45: 211–227.
- 54. Robinson JT (1956) The dentition of the Australopithecinae. Pretoria: Transvall Museum. 179 p.
- 55. Hillson S (1996) Dental Anthropology. Cambridge: Cambridge University Press. 392 p.
- 56. Kanazawa E, Sekikawa M, Ozaki T (1990) A quantitative investigation of irregular cuspules in human maxillary permanent molars. Am J Phys Anthropol 83: 173–180. doi: 10.1002/ajpa.1330830205
- 57. Scott GR (1980) Population variation of Carabelli’s trait. Hum Biol 52: 63–78.
- 58. Guatelli-Steinberg D, Irish JD (2005) Brief Communications: Early Hominin Variability in First Molar Dental Trait Frequencies. Am J Phys Anthropol 128: 477–484. doi: 10.1002/ajpa.20194
- 59. Orban R, Semal P, Twiesselmann F (2001) Sur la biométrie des mandibules et des dents humaines d’Ishango (LSA, République Démocratique du Congo). Bull Mém Soc Anthropol Paris 13: 97–109.
- 60. Quam R, Bailey S, Wood B (2009) Evolution of M1 crown size and cusp proportions in the genus Homo. J Anat 214: 655–670. doi: 10.1111/j.1469-7580.2009.01064.x
- 61. Olejniczak AJ, Smith TM, Feeney RNM, Macchiarelli R, Mazurier A, et al. (2008) Dental tissue proportions and enamel thickness in Neandertal and modern human molars. J Hum Evol 55: 12–23. doi: 10.1016/j.jhevol.2007.11.004
- 62. Olejniczak AJ, Tafforeau P, Feeney RNM, Martin LB (2008) Three-dimensional primate molar enamel thickness. J Hum Evol 54: 187–195. doi: 10.1016/j.jhevol.2007.09.014
- 63. Smith TM, Olejniczak AJ, Martin LB, Reid DJ (2005) Variation in hominoid molar enamel thickness. J Hum Evol 48: 575–592. doi: 10.1016/j.jhevol.2005.02.004
- 64. Kono RT (2004) Molar enamel thickness and distribution patterns in extant great apes and humans: new insights based on a 3-dimensional whole crown perspective. Anthropol Sci 112: 121–146. doi: 10.1537/ase.03106
- 65. Smith TM, Olejniczak AJ, Zermeno JP, Tafforeau P, Skinner MM, et al. (2012) Variation in enamel thickness within the genus Homo. J Hum Evol 62: 395–411. doi: 10.1016/j.jhevol.2011.12.004
- 66. Zanolli C, Bayle P, Macchiarelli R (2010) Tissue proportions and enamel thickness distribution in the early Middle Pleistocene human deciduous molars from Tighenif, Algeria. C R Palevol 9: 341–348. doi: 10.1016/j.crpv.2010.07.019
- 67. Grine FE, Martin LB (1988) Enamel Thickness and development in Australopithecus and Paranthropus. In: Grine FE, editor. Evolutionary History of the “Robust” Australopithecines. New York: Aldine de Gruyter. PP. 3–42.
- 68. Olejniczak AJ, Smith TM, Skinner MM, Grine FE, Feeney RNM, et al. (2008) Three-dimensional molar enamel distribution and thickness in Australopithecus and Paranthropus. Biol Lett 4: 406–410. doi: 10.1098/rsbl.2008.0223
- 69. Skinner MM, Gunz P, Wood BA, Hublin JJ (2009) Discrimination of extant Pan species and subspecies using the enamel-dentine junction morphology of lower molars. Am J Phys Anthropol 140: 234–243. doi: 10.1002/ajpa.21057
- 70. Dechamps R, Meas F (1990) Woody Plant Communities and Climate in the Pliocene of the Semliki Valley, Zaire. In: Boaz NT, editor. Evolution of Environments and Hominidae in the African Western Rift Valley. Martinsville: Virginia Museum of Natural History. PP. 71–94.
- 71. Kirchner MT, Edwards HGM, Lucy D, Pollard AM (1997) Ancient and Modern Specimens of Human Teeth: a Fourier Transform Raman Spectroscopic Study. J Raman Spectrosc 28: 171–178. doi: 10.1002/(sici)1097-4555(199702)28:2/3<171::aid-jrs63>3.0.co;2-v
- 72. Ullrich CG, Binet EF, Sanecki MG, Kieffer SA (1980) Quantitative assessment of the lumbar spinal canal by computed tomography. Radiology 134: 137–143.
- 73. Coleman MN, Colbert MW (2007) Technical note: CT thresholding protocols for taking measurements on three-dimensional models. Am J Phys Anthropol 133: 723–725. doi: 10.1002/ajpa.20583
- 74. Martin L (1983) The relationships of the later Miocene Hominoidea. PhD University College London. 450 p.
- 75. Tafforeau P (2004) Aspects phylogénétiques et fonctionnels de la microstructure de l’émail dentaire et de la structure tri-dimentionnelle des molaires chez les primates fossiles et actuels: apports de la microtomographie à rayonnement X synchrotron. PhD University of Montpellier II. 284 p.
- 76. Olejniczak AJ (2006) Micro-Computed Tomography of Primate Molars. PhD Stony Brook University. 242 p.
- 77. Wood B (1991) Koobi Fora Research Project, Volume 4, Hominid Cranial Remains. Oxford: Oxford University Press. 466 p.
- 78. Clarke RJA (2012) Homo habilis maxilla and other newly-discovered hominid fossils from Olduvai Gorge, Tanzania. J Hum Evol 63: 418–428. doi: 10.1016/j.jhevol.2011.11.007
- 79. Martin R (1914) Lehrbuch der Anthropologie in systematischer Darstellung : mit besonderer Berücksichtigung der anthropologischen Methoden für Studierende Ärzte und Forschungsreisende. Stuttgart: Jena Verl. von Gustav Fischer. 1168 p.
- 80. Grine FE (2005) Enamel thickness of deciduous and permanent molars in modern Homo sapiens. Am J Phys Anthropol 126: 14–31. doi: 10.1002/ajpa.10277
- 81. Cleuvenot E, Houët F (1993) Proposition de nouvelles équations d’estimation de stature applicables pour un sexe indéterminé, et basées sur les échantillons de Trotter et Gleser. Bull Mém Soc Anthropol Paris 5: 245–255. doi: 10.3406/bmsap.1993.2354
- 82. Macho GA, Berner ME (1993) Enamel Thickness of Human Maxillary Molars. Am J Phys Anthropol 92: 189–200. doi: 10.1002/ajpa.1330920208
- 83. Bookstein FL (1997) Morphometric Tools for Landmark Data. Geometry and Biology Cambridge: Cambridge University Press. 456 p.
- 84. Gunz P, Mitteroecker P, Bookstein FL (2005) Semilandmarks in Three Dimensions. In: Slice DE, editor. Modern Morphometrics in Physical Anthropology. New York: Kluwer Academic/Plenum Publishers. PP. 73–98.