Abstract
Although modern humans left Africa multiple times over 100,000 years ago, those broadly ancestral to non-Africans dispersed less than 100,000 years ago1. Most models hold that these events occurred through green corridors created during humid periods because arid intervals constrained population movements2. Here we report an archaeological site—Shinfa-Metema 1, in the lowlands of northwest Ethiopia, with Youngest Toba Tuff cryptotephra dated to around 74,000 years ago—that provides early and rare evidence of intensive riverine-based foraging aided by the likely adoption of the bow and arrow. The diet included a wide range of terrestrial and aquatic animals. Stable oxygen isotopes from fossil mammal teeth and ostrich eggshell show that the site was occupied during a period of high seasonal aridity. The unusual abundance of fish suggests that capture occurred in the ever smaller and shallower waterholes of a seasonal river during a long dry season, revealing flexible adaptations to challenging climatic conditions during the Middle Stone Age. Adaptive foraging along dry-season waterholes would have transformed seasonal rivers into ‘blue highway’ corridors, potentially facilitating an out-of-Africa dispersal and suggesting that the event was not restricted to times of humid climates. The behavioural flexibility required to survive seasonally arid conditions in general, and the apparent short-term effects of the Toba supereruption in particular were probably key to the most recent dispersal and subsequent worldwide expansion of modern humans.
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Data availability
Major and trace element data for the SM1 YTT samples are provided in Supplementary Tables 2–4. Data for ESR dating are provided in Supplementary Table 5. Data for the SM1 stone points are provided in Supplementary Table 6. Palaeomagnetic data are provided in Supplementary Table 13. Isotopic data for the fossil and modern specimens are provided in Supplementary Tables 14, 18 and 23. Supplementary files for the SM1 points shown in Fig. 3 with 3D files, photographs and drawings are provided online (https://doi.org/10.18738/T8/WV9CLN). All other data supporting the findings of this study are available on request from the corresponding author. The artefacts and faunal remains from SM1 are accessioned in the National Museum of Ethiopia, Addis Ababa, Ethiopia.
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Acknowledgements
We thank the Ethiopian Heritage Authority and Ministry of Tourism for permission to conduct our ongoing field research in the Blue Nile Basin; the Director and staff of the National Museum of Ethiopia, Addis Ababa, for their assistance with collections and research space; and the staff from the North Gondar Zone Culture and Tourism Office (Gondar), the Quara Wereda Culture and Tourism Office (Gelegu), especially L. Andargie of the Amhara National Regional State Culture, Tourism and Parks Development Bureau (Bahir Dar) for logistical support and assistance in the field; the Ethiopia Ministry of Mines and Petroleum for permission to export rock samples; the Ethiopian Wildlife Conservation Authority for permission to export modern OES fragments; G. Meskel, Y. Sidwata, A. Kebede, Zakariyyā, B. Meskel Ghebrye, Lagoambasee and Romadad for providing critical local support; students from Addis Ababa University, Bahir Dar University, Colorado State University, Iowa State University, Southern Methodist University, The Liberal Arts and Science Academy, The University of Alabama, The University of Nevada-Las Vegas, The University of Texas at Austin, The University of Texas at San Antonio, University of Gondar, Washington University and Williams College for assisting with data collection in the field and laboratory; D. Graf for assistance with mollusc identifications; D. Pleurdeau for permission to use his measurements of the Porc Epic points; G. Anenia for sketching the points; M. Hersh for reviewing the statistics; and the people of the Shinfa region for their hospitality, friendship and support. The project received funding from the National Science Foundation (9726900, 0921009, 1460986, 1724512 and 9151111), the Leakey Foundation, McMaster University, National Geographic Society, Williams College and The University of Texas at Austin.
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J.K. and L.C.T. conceived the project. G.A.K., J.K., L.C.T., M.F., N.J.T., N.A.R., Y.L.H. and J.J. performed geological sampling and/or analyses. R.J., M.R., E.I.S., M.B., C.J.C., J.N.H., C.W.M. and J.K. performed YTT analysis and/or sample collection. N.D.L. and A. Skinner performed ESR dating. T.E.C., B.A.N., N.J.T., H.W., D.Y., J.W.C., M.F.F., S.M.M., T.S.M., M.C.P., M.B., C.E., N.J.F., T.G., B.H.I, A. Sollenberger, J.S., K.d.l.C.M., J.V., S. Yanny and J.K. performed stable-isotope sampling and/or analyses. C.A.D., D.T., J.K., L.C.T., B.A.N., K.O., D.Y., L.W., A.G. and S. Yirga performed faunal analyses. M.P. performed bone-surface modification analysis. J.K., L.C.T., M.K., A.N., T.N., S. Melaku, K.J.R. and L.M.T. performed analyses and/or visualization of stone tools. J.K., L.C.T., C.A.D., M.F., M.K., B.A.N., A.N., T.N., D.T., J.W.C., M.F.F., T.H., C.K., N.D.L., S. Melaku, S.M.M., S. Millonig, M.C.P., A. Skinner, A.K.T., A.W., E.A., A.A.D., D.D., M.E., F.F., Y.L.H., B.H.I., J.J., S. Mattox, K.d.l.C.M., G.M., K.P., A.R., P.S., J.V., L.W., M.Y. and S. Yanny performed SM1 data collection and curation, with supervision by L.C.T., J.K., B.A.N., C.K., A.K.T., A.W., D.D. and F.F. J.K. wrote the manuscript with input from L.C.T., C.A.D., T.E.C., M.F., R.J., M.K., G.A.K., B.A.N., M.P., E.I.S., N.J.T., H.W., D.Y., J.N.H., A. Skinner, A.W., C.J.C., F.F., C.W.M. and J.V.
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Extended data figures and tables
Extended Data Fig. 1 SM1 geologic setting.
a,b, The Shinfa River is entrenched in the basal flows of the Oligocene Ethiopian Flood Basalt Province (EFBP). Ancient sediments at SM1 consisting of terrace deposits and a gravel bar are exposed on the right bank (bases unknown, dotted lines), and terrace deposits and oxbow lake sediments on the left bank. The Youngest Toba Tephra (YTT, stars) is found on the left bank in trench 5 (Supplementary Fig. 4), on the right bank in trench 2 (Supplementary Fig. 5), and SM1 (see Fig. 2). A-B is cross section. c, Measured and described sedimentological section of trench 2 in proximity to SM1 contains YTT (star, sample Tr2-3) and consists of basal gravel and sand deposits of the ancestral Shinfa River fining upward and laterally as overbank flood deposits comprised of sandy mud and mud, that d, continue into SM1 (north wall of central units, see Fig. 2a), with individual uniformly muddy overbank flood events separated by depositional disconformities. The gird system uses UTM (WGS84 Zone N37P) coordinates in metres (north-south is vertical, east-west is horizontal).
Extended Data Fig. 2 SM1 excavation plan view.
a, Excavation with outlying test units. Chipped stone and fauna were recovered from all units except Z16-3 in the NE; the area highlighted in blue estimates site area at ~300 m2. b, Plan view of contiguous units in the excavation (central dark area in a) showing mapped items. Blue strip at bottom right is initial slit trench, grey strip at top is trench 1 with YTT (white star, sample SH-1-18-03-02), and yellow horizontal strip is N wall in Fig. 2. Area outlined in yellow in a, is E wall in Extended Data Fig. 3. The gird system uses UTM (WGS84 Zone N37P) coordinates in metres (north-south is vertical, east-west is horizontal).
Extended Data Fig. 3 SM1 excavation east wall with YTT.
a, Mapped chipped stone and faunal items (number of individual specimens, NISP) back plotted onto the eastern wall with vertical breaks representing depositional disconformities, and YTT interval shown as red horizontal overlay. b, Same plot showing faunal items only indicates that the frequency of fish (blue solid circles) increases during the YTT interval relative to terrestrial fauna (solid green right triangles) and then returns to pre-YTT levels (see Fig. 5 and Supplementary Table 21). SM1 was intensively occupied before, during, and after YTT, and the site appears to have been abandoned later in time, but higher levels of the terrace to the north have not been excavated. YTT interval illustrated by red horizontal overlay is 31 cm thick at SM1, and arrows indicate location of sample SH-1-18-03-02 (left), with sample Tr2-3 located in trench 2 ~ 20 m to W (right) (Supplementary Fig. 5 and Extended Data Fig. 4). Items recovered from screen wash plotted by metre level at centre of their grid square. Eastern grid squares in this plot are outlined in yellow in Extended Data Fig. 2a. The gird system uses UTM (WGS84 Zone N37P) coordinates in metres, with only northing values shown here.
Extended Data Fig. 4 YTT stratigraphic correlation with trenches and SM1.
Measured and sampled geologic sections include trench 5 on left bank, and trenches 2-4 and SM1 on the right bank of the Shinfa River, with YTT occurrences show by white stars (see Extended Data Fig. 1). The 46 cm thick interval of the YTT isochron in trench 5 (samples TP28, TP29, TP31, and TP32) is shown extended to the NE to correlate with the 31 cm thick interval of YTT between trench 2 (sample Tr2-3) and SM1 (sample SH-1-18-03-02). Sediments from the lowest and uppermost portions of trench 5, the lower portion of trench 2, and trenches 3 and 4, were processed but did not produce cryptotephra. The gird system uses UTM (WGS84 Zone N37P) coordinates in metres, with only easting values shown here.
Extended Data Fig. 5 Correlation of YTT samples using paleomagnetic stratigraphy.
Oriented samples for paleomagnetic analyses were collected from a, trench 5 on the left bank of the Shinfa River, and b, trenches 2-4 and SM1 on the right bank (Extended Data Figs. 1 and 4, Supplementary Figs. 4 and 5, Supplementary Table 13, and Supplementary Note 2). All sites are normal polarity, and we hypothesize that the values following demagnetization preserve evidence of secular variation in the Earth’s magnetic field. Sites with the shallowest virtual geomagnetic pole (VGP) in both sections as documented by the mean of three samples (solid large circle) occur below the lowest occurrence of YTT (a, trench 5, red horizontal overlay; b, trenches 2–4 and SM1, blue horizontal overlay) are used for the correlation (dashed horizontal line marked by black arrows). The shallow VGP sites are TP26 in trench 5 at 2.68 m that is 30 cm below site TP28 with the lowest YTT, and site Tr2-1 in trench 2 at 581.222 m that is 36 cm below site Tr2.3 with the lowest YTT. The interval with YTT in a, trench 5 is 46 cm in thickness (see Supplementary Fig. 4), while in b, this interval is between sample Tr2-3 in trench 2 (Extended Data Fig. 1c and Supplementary Fig. 5), and SH-1-18-3-2 in SM1 (originally in trench 1, see Fig. 2 and Extended Data Fig. 2) is 31 cm in thickness. Key: grey solid circle, single sample; large red or blue solid circle, mean of three or more samples; red or blue diamond, mean of two samples.
Extended Data Fig. 6 Youngest Toba tephra chemistry.
a, SiO2 vs. FeO plot compares Shinfa River shards to YTT and volcanoes in Africa, Antarctica, the Mediterranean, and Turkey. Red box in lower right of plot enlarged in b, illustrates overlap between Shinfa River shards and YTT. c, CaO vs. FeO plot compares Shinfa River shards to Erciyes Dağı and YTT; d, Trace elements normalized to primitive mantle compares Shinfa River shards to YTT. Primitive mantle data in Sun and McDonough53. See Supplementary Tables 2–4 and Supplementary Note 2.
Extended Data Fig. 7 RMA regression of archaeological and ethnographic arrowheads and dart points with SM1 and African MSA points.
Reduced major axis (RMA) linear regressions for a primarily North American sample of archaeological and ethnographic arrowheads and dart points7,8 demonstrate that arrowheads (R2 = 0.8046) differ from dart points (R2 = 0.7399) in having a smaller tip cross-sectional perimeter (TCSPt, triangular method6) relative to tip cross-sectional area (TCSA), with a two-tailed t-test showing that the slopes differ at p = 0.073 (DF = 168, t statistic = 1.8023). While not statistically significant at p < 0.05 (0.05 <p < 0.10), this result offers support for the theoretical basis of the shape design distinctions between these two types of projectile points, and how they are related to the intrinsic differences between the propulsive, aerodynamic, and resultant penetration properties of these mechanical projectile delivery systems5. Note that the largest arrowheads (black arrows) plot with the MSA points and fall outside the ± 95% RMA confidence limits (dotted lines) of both darts and arrowheads but are closer to arrowheads. References: arrowheads and dart points7,8; SM1 points see Supplementary Table 6; Aduma A5 and A810; and Sibudu Cave102. See the ‘Statistics and plots’ section of the Methods.
Extended Data Fig. 8 TCSA x TCSPt of archaeological and ethnographic arrowheads and dart points and SM1 points.
a, Plot of tip cross-sectional area (TCSA) by tip cross-sectional perimeter (TCSPt, triangular method6) for a primarily North American sample of archaeological and ethnographic arrowheads and dart points7,8 demonstrates some overlap in size, but for a given TCSA, medium to large arrowheads generally have a relatively smaller TCSPt than medium to large dart points. b, SM1 points (Supplementary Table 6, n = 26) resemble arrowheads more than dart points in this feature, and c, plot below and to the right of dart points, and d, fill the gap between the medium and largest (black arrows) arrowheads.
Extended Data Fig. 9 Diagnostic impact fracture (DIF) damage.
a–f, Isolated distal tips and g–l, proximal bases recovered from SM1 preserve bending-snap diagnostic impact fracture (DIF) damage that is consistent with projectile use12 (see Supplementary Table 6). It is hypothesized that the broken distal point tips were returned to SM1 embedded in carcasses, and ended up on the ground after the carcass was processed, while the bases were broken during use, returned to SM1 still hafted to the arrow shaft, and removed from the shaft to which a new point was hafted, thus recycling the shaft, with the broken base then discarded or reused. See Supplementary Note 4 for additional discussion. Specimen number and find elevation: a, W14-17-262, 581.327 m; b, W14-6-270, 581.332 m; c, SM1-646, surface; d, SM1-992, surface; e, W15-18-362, 581.558 m; f, W15-18-461, 581.464 m; g, SM1-389, surface, and see Fig. 3f and Supplementary Data; h, W15-23-90, 581.789 m; i, W15-12-75, 581.426 m; j, SM1-492, surface; k, SM1-10, surface; and l, W15-12-38, 581.564 m.
Extended Data Fig. 10 Use wear.
Use wear was studied with optical microscopy. Point SM1-2 (surface find, Fig. 3i) illustrates typical results. SM1-2 preserves a, impact fracturing and cutting wear at the tip (yellow box enlarged at middle and right) with a DIF bending fracture with hinge termination (white arrows, see the Supplementary Data), and b, hafting marks at the base (blue box enlarged at middle and right). Similar distinctive use wear and DIF are preserved on many of the SM1 points (Fig. 3, Extended Data Fig. 9, and Supplementary Table 6) that, along with their standardized and triangular symmetrical shape, and geometries closer to arrowheads than dart points (Extended Data Figs. 7 and 8, Supplementary Figs. 10 and 11), suggest that the SM1 points are likely arrowheads. See the ‘Use-wear analysis’ section of the Methods and Supplementary Note 4.
Extended Data Fig. 11 SM1 fauna.
Variety of faunal specimens displaying taxonomic breadth and typical preservational states. a, Bovid cf. Gazella sp., left proximal femur, posterior view (W14-4-197, 580.945 m level). b, Warthog, Phacochoerus, left lower third molar, occlusal (top) and left lateral (bottom) views (SM1-311, surface; see Supplementary Table 14 for isotope values, and Supplementary Fig. 17). c, Grivet monkey, Chlorocebus cf. aethiops, adult (epiphysis fused) right proximal humerus (SM1-250, surface); see Supplementary Fig. 12 for analysis of bone surface modification marks on shaft shown in close ups centre and right. d, Guinea fowl, Numida meleagris, right humerus with possible cut and/or tooth marks in close up (W14-25-834, 581.333 m). e, Ostrich, Struthio camelus, burned eggshell fragments (W15-23-153, 581.600 m, screen wash). f, Snake vertebrae, ventral view, cf. Python sebae (W14-16-178, 581.449 m). g, Right fish dentaries (articular and dentary): modern Clarius gariepinus from Gelegu River (left, fish total length 26 cm), and much larger partial fossil dentary (right, incomplete toward symphysis) of Clarius gariepinus. Fossil was found as four separate fragments (W15-22-2: 581.896 m; W15-22-11: 581.898 m; W15-22-21: 581.843 m; and W15-22-44: 581.876 m) that conjoin with one another at clean, sharp breaks. See Supplementary Fig. 3, fish #4, for vertical and horizontal locations of these fragments in the excavation. h, Fish skeletal fragments recovered from a single bin of screen wash matrix illustrates typical density of fish remains at SM1 (blue ellipse: sorted head plate fragments; red square: sorted calcined and heated fragments) (Z13-4-83, 581.957 m). i, Frog left innominate (SM1 W14-4-114, 581.131 m). j, Siluriform cf. Synodontis right cleithrum with articulated and erect pectoral spine with broken tip (yellow arrow, W14-25-536, 581.457 m). k, Juvenile mollusk, Coelatura cf. aegyptiaca (X15-20-473, 581.623 m).
Extended Data Fig. 12 Fossil and modern bovid dental enamel δ18O.
Fossil bovids from SM1, seven MSA and MSA–LSA archaeological sites in East Africa and the Arabian Peninsula, and modern bovids from select East African locations display a wide range of δ18O(VPDB) ‰ values. SM1 bovids have among the highest δ18O values, and two-tailed t-tests assuming equal variance show that the only archaeological site or modern location that SM1 is not significantly different from is Turkana (p > 0.05; p = 0.0873). Red horizontal bar is the 50% sample for SM1. Site, age, sample size for biologically independent fossil specimens, and references: SM1, ~74 ka, Supplementary Table 14 (n = 18); Karungu, Kenya, ~45 to 94 ka (n = 20)26; Kibish Member III, Ethiopia, ~104 ka (n = 10)27; Porc Epic, Ethiopia, ~40 to 100 ka (n = 41)28; Lukenya Hill, Kenya, ~15 to 46 ka (n = 74)28; Kalemba Rock Shelter, Zambia, ~8 to 40 ka (n = 40)28; Lake Victoria Islands, ~45 to 100 ka (n = 44)29; Ti’s al Ghadah, Arabian Peninsula, ~300 to 500 ka (n = 17)30. Sample size for biologically independent modern specimens32: Turkana (n = 35); Awash (n = 12); Mago (n = 14); Serengeti (n = 47); Nakuru (n = 35); Athi (n = 115); Kidepo (n = 17); Aberdares (n = 13). See Supplementary Table 16 for statistics. Dot and box plot defined in the ‘Statistics and plots’ section of the Methods.
Extended Data Fig. 13 Water deficits for modern East African locations, and δ18O for modern and fossil bovids from MSA and MSA–LSA archaeological sites.
Bovids from modern African locations with highest δ18O values plotted as first and third quartiles (n ≥ 10)32. Reduced major axis (RMA) regressions of first and third quartile values highlight relationship between δ18O and water deficit. Bovids from SM1 and seven MSA and MSA–LSA sites shown above plot as first and third quartiles (all n ≥ 10). SM1 overlaps with modern Turkana with highest δ18O values (vertical bars), and less with Awash and Mago. Estimated SM1 water deficit falls between Turkana and the other modern locations. Modern Shinfa cows and goat plotted at top preserve high δ18O values (Supplementary Note 8). Site, age, sample size for biologically independent fossil specimens, and references: SM1, ~74 ka, Supplementary Table 14 (n = 18); Karungu, Kenya, ~45 to 94 ka (n = 20)26; Kibish Member III, Ethiopia, ~104 ka (n = 10)27; Porc Epic, Ethiopia, ~40 to 100 ka (n = 41)28; Lukenya Hill, Kenya, ~15 to 46 ka (n = 74)28; Kalemba Rock Shelter, Zambia, ~8 to 40 ka (n = 40)28; Lake Victoria Islands, ~45 to 100 ka (n = 44)29; Ti’s al Ghadah, Arabian Peninsula, ~300 to 500 ka (n = 17)30. Sample size for biologically independent modern specimens from Shinfa: cows (n = 3), goat (n = 1) (Supplementary Table 14); modern locations32: Turkana (n = 35); Awash (n = 12); Kidepo (n = 17); Tsavo (n = 58); Queen Elizabeth (n = 44); Mago (n = 14); Laikipia (n = 97); Athi (n = 115); Serengeti (n = 47); Nakuru (n = 35); Bale (n = 12); Ituri (n = 10); Aberdares (n = 13); and Kibale (n = 11).
Supplementary information
Supplementary Information
Supplementary Notes 1–9, Supplementary References, Supplementary Figs. 1–18 and Supplementary Tables 1–23.
Supplementary Data
Repository link for 3D surface scans of the 13 points from SM1 illustrated in Fig. 3. The 3D scans of the points are interactive objects. Open the file in Adobe Reader, and click on the image of the point at left. It is a 3D object and, in a few seconds, an interactive menu will open, and the viewer will be able to zoom in/out, rotate, view cross-sections and so on. Moreover, photographs of the dorsal and ventral surfaces are included at the top right, with drawings shown at the bottom right. Supplementary Table 6 includes the description of the metrics, DIF and use wear. Each point is also available in the .ply file format for viewing and/or 3D printing.
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Kappelman, J., Todd, L.C., Davis, C.A. et al. Adaptive foraging behaviours in the Horn of Africa during Toba supereruption. Nature 628, 365–372 (2024). https://doi.org/10.1038/s41586-024-07208-3
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DOI: https://doi.org/10.1038/s41586-024-07208-3
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