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Lakeside cemeteries in the Sahara: 5000 years of holocene population and environmental change - PubMed

  • ️Tue Jan 01 2008

Lakeside cemeteries in the Sahara: 5000 years of holocene population and environmental change

Paul C Sereno et al. PLoS One. 2008.

Abstract

Background: Approximately two hundred human burials were discovered on the edge of a paleolake in Niger that provide a uniquely preserved record of human occupation in the Sahara during the Holocene ( approximately 8000 B.C.E. to the present). Called Gobero, this suite of closely spaced sites chronicles the rapid pace of biosocial change in the southern Sahara in response to severe climatic fluctuation.

Methodology/principal findings: Two main occupational phases are identified that correspond with humid intervals in the early and mid-Holocene, based on 78 direct AMS radiocarbon dates on human remains, fauna and artifacts, as well as 9 OSL dates on paleodune sand. The older occupants have craniofacial dimensions that demonstrate similarities with mid-Holocene occupants of the southern Sahara and Late Pleistocene to early Holocene inhabitants of the Maghreb. Their hyperflexed burials compose the earliest cemetery in the Sahara dating to approximately 7500 B.C.E. These early occupants abandon the area under arid conditions and, when humid conditions return approximately 4600 B.C.E., are replaced by a more gracile people with elaborated grave goods including animal bone and ivory ornaments.

Conclusions/significance: The principal significance of Gobero lies in its extraordinary human, faunal, and archaeological record, from which we conclude the following: The early Holocene occupants at Gobero (7700-6200 B.C.E.) were largely sedentary hunter-fisher-gatherers with lakeside funerary sites that include the earliest recorded cemetery in the Sahara.Principal components analysis of craniometric variables closely allies the early Holocene occupants at Gobero with a skeletally robust, trans-Saharan assemblage of Late Pleistocene to mid-Holocene human populations from the Maghreb and southern Sahara.Gobero was abandoned during a period of severe aridification possibly as long as one millennium (6200-5200 B.C.E).More gracile humans arrived in the mid-Holocene (5200-2500 B.C.E.) employing a diversified subsistence economy based on clams, fish, and savanna vertebrates as well as some cattle husbandry.Population replacement after a harsh arid hiatus is the most likely explanation for the occupational sequence at Gobero.We are just beginning to understand the anatomical and cultural diversity that existed within the Sahara during the Holocene.

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Conflict of interest statement

Competing Interests: The authors have declared that no competing interests exist.

Figures

Figure 1
Figure 1. Location maps and geologic section across principal sites at Gobero.

(A)-Map showing location of the Holocene archaeological site Gobero and the Holocene felsite quarry Alallaka on the border of the Aïr massif. (B)-Geologic map of main paleodune cemetery sites (G1-3) showing transect line connecting 13 geologic sections (see C, E, F) and a portion of a topographic transect (dashed line; see D). (C)-Stratigraphic profile across sites G1-3 based on 13 sections showing the Cretaceous peneplain of the Elrhaz Formation, the Late Pleistocene to early Holocene paleodune deposit, the early to mid-Holocene paleolake deposit, and Recent sand cover (15 times vertical exaggeration). (D)-Topographic transect (dashed line in B) between site G5 and a spillway on the Mazelet fault scarp located 1.3 km to the south (30 times vertical exaggeration). Habitation (3 m) and maximum (8 m) paleolake levels are shown, the latter resulting in inundation of archaeological sites G1-5. (E)-Stratigraphic section of paleolake deposit between sites G1 and G2 with fossiliferous zone limited to the uppermost 5 cm and location of sediment sample for 14C AMS date 75 (Table 2). (F)-Stratigraphic section of paleodune deposit at site G1 showing human skeletons limited to the uppermost 1 m and the location of three OSL samples (Table 1, dates 2–4). Abbreviations: AMS 75, 14C AMS date 75; OSL, optically stimulated luminescence.

Figure 2
Figure 2. Aerial view of Gobero sites.

Aerial view (facing north) of a portion of the Gobero site complex, first discovered in 2000, showing the raised paleodune sites G3 (bottom left, oval) and G2 (bottom right, ridge) situated on the peneplain of the Early Cretaceous (Aptian-Albian) Elrhaz Formation. The 2006 Expedition campsite (middle right) and a Recent barcan dune field are seen in the distance. The prominent edges of the paleodune sites are composed of calcrete (calcite-cemented aeolian sand). An excavation team is present on site G3. Near its right (east) margin, the pit for geologic section 3 is visible (see Figure 1B).

Figure 3
Figure 3. Radiocarbon (14C AMS) dates for human skeletons, ceramics, charcoals, middens, fauna, artifacts and sediment.

Timelines and occupation phases 1–4 are shown at the bottom. Associated chronometric data are compiled in Table 2 using current atmospheric standards . All of the burials that have been dated at Gobero fall within phases 2 and 3, which are shown as green to indicate favorable humid climate conditions; more arid intervals are shown as tan including occupation phases 1 and 4. Multiple dates on individual specimens or features are boxed. A dotted line separates early and mid-Holocene human burials. Abbreviations: B.C.E., before current era (registered to calendar year zero); B.P., before present (1950); G1B8, burial 8 on G1; G1B11, burial 11 on G1; G3B8, burial 8 on G3; K, Kiffian; LT, Late Tenerean; T, Tenerean.

Figure 4
Figure 4. Early Holocene cemetery, burials and skulls.

(A)-Gobero site G3 showing excavated burials (red dots). (B)-Enlarged map of the early Holocene cemetery showing the location of 17 undisturbed burials of skeletons with dark-stained bone (red dots). Five burials (red dot with outer ring) were directly dated to a narrow range of ∼7500±250 years B.C.E. (Figure 2; Table 2). (C)-Skeleton (dark-stained) of an early Holocene adult male (G3B8; ∼7515 B.C.E.) buried in supine, hyperflexed posture with hands over the mouth and feet crossed. Computed-tomography cross-section (below) across the middle of the skeleton (red line) shows the tightly bundled configuration of major limb bones (within a 25 cm×12 cm rectangle) for an adult with stature approximately 2 m. (D)-Skull of early Holocene adult male (as in C) showing long, low calvarium, broad zygomatic width and relatively flat face. (E)-Skull of an early Holocene juvenile (G3B17b; ∼7630 B.C.E; estimated age 5 years) already showing long, low cranial proportions. Scale bar in C equals 13.3 cm for skeleton and 10 cm for CT scan; skull length (glabella-opisthocranion) in D and E equals 190.0 mm and 171.0 mm, respectively. Abbreviations: f, femur, fi, fibula; h, humerus; r, radius; ti, tibia; ul, ulna.

Figure 5
Figure 5. Mid-Holocene burials and skull.

(A)-Top view of mid-Holocene adult male (G1B11; ∼4645 B.C.E.) buried in a recumbent hyperflexed posture. (B)-Bottom view of burial in A showing a mud turtle carapace (Pelusios adansonii) in contact with the ventral aspect of the pelvic girdle. (C)-Skull from burial in A and B showing high calvarium, narrow zygomatic width and more prognathous face. (D)-Mid-Holocene juvenile (G1B2; ∼2835 B.C.E.) with upper arm bracelet of hippo ivory. (E)-Mid-Holocene triple burial involving an adult female (G1B8; ∼3315 B.C.E.) and two juveniles (G1B9, G1B10) with intertwined arms, hands and legs. (F)-Schematic showing skeletal positions in the triple burial with the adult female on right (tan, G1B8) facing juveniles with estimated ages of 8 years (black, G1B9) and 5 years (red, G1B8).

Figure 6
Figure 6. Principal components analysis of craniofacial dimensions among Late Pleistocene to mid-Holocene populations from the Maghreb and southern Sahara.

Plot of first two principal components extracted from a mean matrix for 17 craniometric variables (Tables 4, 7) in 9 human populations (Table 3) from the Late Pleistocene through the mid-Holocene from the Maghreb and southern Sahara. Seven trans-Saharan populations cluster together, whereas Late Pleistocene Aterians (Ater) and the mid-Holocene population at Gobero (Gob-m) are striking outliers. Axes are scaled by the square root of the corresponding eigenvalue for the principal component. Abbreviations: Ater, Aterian; EMC, eastern Maghreb Capsian; EMI, eastern Maghreb Iberomaurusian; Gob-e, Gobero early Holocene; Gob-m, Gobero mid-Holocene; Mali, Hassi-el-Abiod, Mali; Maur, Mauritania; WMC, western Maghreb Capsian; WMI, western Maghreb Iberomaurusian.

Figure 7
Figure 7. Ceramic, lithic, bone and hippo ivory artifacts and ornaments.

(A)-Mid-Holocene adult male (G3B36; ∼3500 B.C.E.) buried with skull resting in a partial ceramic vessel (see B). (B)-Side and magnified view of ceramic vessel (G3-94) under skull (see A) showing rocker stamp decoration. Kiffian tool kit (C–F). (C)-Biserial bone harpoon point with perforated butt (GA154) made from a crocodile dentary. (D)-Uniserial fixed barbed point with notched butt (GA130) made from an artiodactyl long bone. (E)-Bone hook (GA31a). (F)-Crescent-shaped microlith (G1-71b) from site G1 (deflated). Tenerean tool kit (G-I). (G)-Felsite bifacial point (G3-1b) associated with an adult male burial (G3B4). (H)-One (G1-134) of four hollow-based points associated with a mid-Holocene adult female (G1B8; ∼3315 B.C.E.) in a triple burial (Figure 3E, F). (I)-Anterior and magnified view of a felsite adze (GA110c) showing the green color and vesicles common to this source rock. (J)-Amazonite pendant (GA124). (K)-Upper arm bracelet (G1-7) carved in hippo ivory near the distal end of the left humerus in a juvenile burial (G1B2; ∼2835 B.C.E.). (L)-Bead (G3-6 necklace, bead 9) made of hippo ivory showing the paired bite mark from the incisors of a rodent (top, arrow) on a divot removed from the bead margin (bottom). (M)-Anterior and magnified lateral views of a pendant (part of G3-6 necklace) carved in hippo ivory and found in situ on a mid-Holocene adult female (G3B41; ∼3620 B.C.E.). Scale bars equal 5 cm in B and 2 cm in L. Ages given above are from 14C AMS dates on enamel bioapatite and represent the midpoint of the calibrated radiocarbon confidence interval (Table 2). Maximum artifact length is 11.9 cm in C, 13.2 cm in D, 2.0 cm in E, 2.3 cm in F, 2.04 cm in G, 2.0 cm in H, 8.2 cm in I, 4.4 cm in J, 8.4 cm in K, and 8.8 cm in M.

Figure 8
Figure 8. Alallaka, a felsite knapping site on the edge of the Aÿr massif.

(A)-An intrusion of green microcrystalline feldpar, or felsite , is exposed as an oval outcrop approximately 0.8 km in width and 2.5 km in length near the Alallaka wadi on the southeastern edge of the Air massif (an area known as Takolokouzet), situated 160 km north of the Gobero site complex Figure 1A). The exposed rock shows the characteristic green hue, variable lamination, and vesicular texture common to many of the felsite lithics from Gobero. (B)-Abundant debitage as well as large groundstones attest to a longstanding knapping operation at Alallaka. Scale bar equals 3 cm.

Figure 9
Figure 9. Mid-Holocene midden.

Portion of a mid-Holocene midden (midden 4) with matrix removed showing stacking of the valves of the clam Mutela, articulated fish vertebrae, and potsherds (Table 2, dates 42, 43, average midpoint ∼4445 B.C.E.).

Figure 10
Figure 10. Pollen composition in mid-Holocene burials.

(A)-Percentage pollen spectra from three mid-Holocene burials on sites G1 and G3 showing low diversity vegetation and the prevalence of Sahelian phytogeographical character. (B)-Arboreal pollen. (C)-Non-arboreal pollen. Long distance transport is low, as indicated by the paucity of Mediterranean taxa . Crushed or damaged pollen grains that could be identified were summed in the relevant taxa. Only pollen that could not be identified were included in the deteriorated sum. Abbreviations: CONISS, constrained incremental sum of squares; p/g, pollen per gram.

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