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Introduction

The “greening” and ultimate desiccation of the Sahara rank among the most severe climatic fluctuations during the Holocene [1]. Driven by variation in orbital insolation and magnified by feedback between monsoonal rainfall and vegetation [2], ecosystem succession in the Sahara is well known from many lines of evidence such as pollen spectra [3], paleolake levels [4]–[6], and, most recently, high-resolution paleolake sediment cores [7].

Human adaptation during this period of climate fluctuation is best known in the Eastern Sahara to the west of the Nile valley. This region witnessed continuous occupation from 8500 B.C.E., when hunter-gatherers using a distinctive Epipaleolithic tool kit expanded across open grass savanna habitats, to about 3500 B.C.E, when aridification drove pastoralists from most areas of the desert [8]. Occupational patterns in low-lying regions elsewhere in the Sahara most closely resemble the Eastern Sahara during the early Holocene (~8000–7000 B.C.E.), when pottery-producing hunter-fisher-gatherers resided beside paleolakes, utilizing a tool kit including microliths and harpoon points and fish hooks of bone [9]–[11]. By the mid-Holocene, occupational histories diverge in the Central and Western Sahara [12] as a result of distinctive local humid-arid cycles [13]–[15], diversified economies and lifestyles tied to ephemeral paleolakes [10], upland refugia [16] and rivers [17], and marked variation among the human populations themselves [10], [18], [19]. Despite increasing knowledge regarding occupational succession in the Sahara from early to late Holocene [8], [10], [11], [16], [17], that record is based on individual sites that typically preserve short intervals of occupation, include few if any intact burials, and rely largely on indirect dating of human remains and artifacts [20].

We report here on a new site complex called Gobero located at the western tip of the hyperarid Ténéré Desert in the southern Sahara in Niger (Figures 1A, 2). Approximately 200 burials ranging in age over five millennia are present in the upper level of several paleodunes that are situated adjacent to a paleolake deposit. Gobero preserves the earliest and largest Holocene cemetery in the Sahara, opening a new window on the funerary practices, distinctive skeletal anatomy, health and diet of early Holocene hunter-fisher-gatherers, who expanded into the Sahara when climatic conditions were favorable. The site complex also preserves numerous mid-Holocene burials, some indicating funerary rituals with grave inclusions. Associated middens and an exceptional faunal and pollen record provide a chronicle of episodic human occupation in the Sahara under conditions of severe climatic change.

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.

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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).

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Table 1. Optically stimulated luminescence (OSL) dates for paleodune sand.

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Table 2. Ages and associated data for 78 radiocarbon ¹⁴C AMS dates, which are shown graphically in Figure 3 (bottom to top).

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Results and Discussion

Geologic Setting

Gobero is located on the northwestern rim of the Chad Basin, approximately 150 km southeast of the Aïr massif (Figure 1A). Isolated on a vast peneplain of mid-Cretaceous sandstone between fields of migrating barcan dunes (Figure 2), the most important cluster of sites at Gobero is located in low, calcrete-fringed paleodunes that are partially surrounded by paleolake deposits [Figure 1B, C). The paleodunes accumulated at Gobero over a period of at least seven millennia from the Late Pleistocene to the early Holocene (~14,000–7000 B.C.E.), as determined by optically stimulated luminescence (OSL) dating of paleodune sand at various depths (Figure 1F, Table 1). During the best preserved intervals of occupation, the core paleodune sites (G1-3) formed islands that may have been originally partially conjoined as a narrow peninsula into Paleolake Gobero, a shallow, freshwater lake no more than 3 m in depth and 3 km in diameter (Figure 1C, D). The lake occupied a small endorheic basin located on a low rise between drainages southwest to the Niger River and southeast to Paleolake Chad. Fed periodically by surface water from the Aïr massif that pooled against a low east-west fault scarp (Mazelet) immediately to the south, Paleolake Gobero appears to have been more closely associated with the Chad Basin, as there is no trace of the giant catfish (Arius gigas) common to drainages of the Niger [21]. The archaeological sites were submerged when the lake filled to a depth greater than 5 m (Figure 1D). Over time the human bone in submerged burials darkened and hardened to resemble the pyrolusite (MnO₂)-darkened vertebrate bone in the adjacent paleolake deposit.

Model for the Gobero Sequence

Based on geochronological data (Tables 1, 2) with input from archaeological, craniometric, zooarchaeological and archaeobotanical analysis, we divide the record preserved at Gobero into four occupation phases (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 [55]. 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.

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Phase 1—Paleodune Accumulation (14,000–7700 B.C.E.).

Phase 1 is predominantly an arid interval at the close of the Pleistocene and beginning of the Holocene, when dune sands accumulated in the Gobero area over Cretaceous bedrock under climatic conditions characterized by weakened monsoons and the spread of aridification across northern Africa [4]–[6], [12]–[14]. The base of the paleodune deposit at site G1 dates to ~14,000 B.C.E. (Figure 1B, F, section 12; Table 1, dates 3, 4). Although humid intervals are recorded elsewhere in the central Sahara [5], [13], [14] and may have occurred during phase 1 at Gobero, Paleolake Chad never grew to megalake dimensions until later in the early and mid-Holocene [5], [6], and the paleodune sequence at Gobero accumulated without a detectible hiatus. Deflated Ounanian artifacts [22]–[24] were recovered suggesting that during this phase there were transient hunter-gatherers in the Gobero area who seem not to have left any burial record in the lower portion of the paleodune sequence.

Phase 2—Early Holocene Occupation (7700–6200 B.C.E.).

During phase 2, wet climatic conditions attracted a population of hunter-fisher-gatherers to Gobero sites, which served both funerary and habitation functions. In one area of site G3 no larger than 50 m², 17 closely interspaced (≤4 m), undisturbed burials contain dark-stained skeletons composing a cemetery (Figure 4A, B). Direct dates for five of these burials indicate an age of ~7500 B.C.E. and range over only ~250 years (Figure 3; Table 2, dates 1–7). This cemetery is considerably larger than a small cluster of burials at a somewhat younger site along the upper Nile (El Damer) [11] and predates by three millennia the oldest cemetery in Egypt's Western Desert (Gebel Ramlah) [25]. Phase 2 is delimited in time by burials within site G3 with direct dates (Table 2, dates 1, 7), the oldest a subadult individual in the cemetery (7730–7580, midpoint 7655 B.C.E.) and the youngest an adult located nearby (6380–6210, midpoint 6295 B.C.E.).

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.

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Phase 2 peoples are tall in stature, approaching two meters for both males and females. Hyperflexed, supine burial postures predominate, their compact configuration and anatomical articulation suggesting that their bodies were tightly bound with animal skin, ligament or basketry binding, although no trace of these perishable materials are preserved (Figure 4C). Their crania are long and low and are characterized by a distinct occipital bun, flattened sagittal profile, pentagonal posterior outline, broad proportions across the zygoma and interorbital region, broad nasal aperture, and negligible alveolar prognathism (Figure 4D), features that are apparent in juveniles as young as four years of age (Figure 4E) and absent in skulls from mid-Holocene burials (Figure 5C).

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).

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Craniometric data from seven human groups (Tables 3, 4) were subjected to principal components analysis, which allies the early Holocene population at Gobero (Gob-e) with mid-Holocene “Mechtoids” from Mali and Mauritania [18], [26], [27] and with Late Pleistocene Iberomaurusians and early Holocene Capsians from across the Maghreb (see cluster in Figure 6). The striking similarity between these seven human populations confirms previous suggestions regarding their affinity [18] and is particularly significant given their temporal range (Late Pleistocene to mid-Holocene) and trans-Saharan geographic distribution (across the Maghreb to the southern Sahara).

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.

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Table 3. Nine human populations sampled for craniometric analysis ranging in age from the Late Pleistocene (ca. 80,000 BP, Aterian) to the mid-Holocene (ca. 4000 BP) and in geographic distribution across the Maghreb to the southern Sahara [18], [19], [26], [27], [54].

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Table 4. Craniometric means for human samples.

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Microliths, bone harpoon points and hooks, and ceramics with dotted wavy-line and zigzag impressed motifs were found in the burial fill, in an associated refuse area, and in nearby paleolake deposits (Figure 7C–F). These artifacts exhibit attributes of the Kiffian technocomplex, named after the type site Adrar-n-Kiffi at Adrar Bous some 500 km to the north [28], [29]. Direct dates on bone harpoon points and plant temper in Kiffian sherds confirm the association of several of these artifacts with this occupational phase (Figure 3; Table 2, dates 26–28, 64, 65). Nile perch (Lates niloticus) and large catfish dominate the midden fauna, which also includes bones and teeth from hippos, several bovids, small carnivores, softshell turtles and crocodiles (Table 5, refuse area 5). The burial density, tool kit, ceramics, and midden fauna suggest a largely sedentary population with a subsistence economy based on fishing and on hunting of a range of savanna vertebrates.

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.

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Table 5. Faunal list at Gobero showing taxa recorded at archaeological sites (G1-3), in early and mid-Holocene middens (middens 1–4, refuse area 5), and in the Gobero area (in paleolake deposits or on deflation surfaces).

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Pollen from phase 2 burials at site G3 indicates an open, low-diversity savanna with grasses and sedges, and an arboreal component including fig (Ficus) and tamarisk (Tamarix). Hydrophytes and rushes (Juncus) suggest the presence of permanent water and marshy habitats [15], [30]. Nevertheless, xerophytes including saltbushes (Chenopodiaceaea) are significant, indicating that sandy habitats were also present, although perhaps distant, in the region.

Toward the end of phase 2 (~6500–6300 B.C.E.), the level of Paleolake Gobero rose, at least episodically, submerging the paleodunes and forcing the relocation of occupants (Figure 1D). Well-aerated permanent water at depths of 5 m or more are suggested by large vertebrae (up to 5 cm diameter) of the Nile perch (Lates niloticus), which correspond to a body length of up to 2 m [31]. These vertebrae were found in situ in paleolake sediments and directly dated to the end of this phase (Figure 3; Table 2, dates 57, 58; midpoint average 6525 B.C.E.). The darkened bone color of all human skeletons in phase 2 burials is indicative of sustained inundation. Inundation, nevertheless, may have been episodic, as a dark-stained human skeleton (G3B28), Kiffian potsherd, refuse area, and hartebeest skeleton (Alcelaphus buselaphus) are also directly dated to this interval (Figure 3; Table 2, dates 8, 28, 40, 41, 56; midpoint range 6540–6295 B.C.E.).

Because spillways external to the restricted catchment for Paleolake Gobero may have kept inundation levels under 10 m (Figure 1D), it is possible that floodwaters may not have displaced lakeside occupants by a long distance or over a long temporal span. The inundation history at Gobero is doubtless complex, as the earliest mid-Holocene burials are also variegated or darkly stained (Table 2, dates 9–13; midpoint range 4825–3860 B.C.E.). Resolving additional inundation events of short duration will require further direct dates on paleolake fauna and sediments.

Occupational Interruption (6200–5200 B.C.E).

A harsh arid interval separates early and mid-Holocene populations at Gobero, when the paleolake appears to have dried out and the area abandoned. Although we have no means to directly assess aridity, no terrestrial or aquatic vertebrates or lakebed sediment have been dated to this interval, which lasted approximately one millennium (Figure 3). The only specimens dated within this interval were found in the paleolake deposit and consist of a cluster of the small gastropod Melanoides tuberculata, a species that prefers periodically flooded habitats to permanent water bodies.

This occupational hiatus correlates well with the “arid interruption” in the central Sahara [12], a somewhat shorter interval (~6400–6000 B.C.E.; ~400 yr) of severe climatic deterioration across the Chad Basin [5], [12] linked to cooling events in the North Atlantic [13], [14]. This overlaps the early portion of the occupational hiatus at Gobero, the beginning of which is set after the youngest burial dated so far in occupation phase 2 (Figure 3; Table 2, date 8, 6380–6210 B.C.E., midpoint 6295 B.C.E.). The end of the occupational interruption is set just before direct dates that indicate the return of humid conditions, including paleolake sediment 20–25 cm below the fossil-rich zone (Figure 1B, E, section 9; Figure 3; Table 2, date 75, 5550–4750 B.C.E., midpoint 5150 B.C.E.), a ceramic sherd from burial fill in site G1 (Figure 3; Table 2, date 29, 5220–5000 B.C.E., midpoint 5110 B.C.E.), and the oldest burial dated so far from occupation phase 3 (Figures 3, 5A–C; Table 2, enamel dates 9, 10, midpoint average 4635 B.C.E.).

Phase 3—Mid-Holocene Occupation (5200–2500 B.C.E.).

Phase 3 is a long interval over two millennia in length that witnessed the return of humid conditions and the re-occupation of Gobero by humans that account for approximately one-half of excavated burials (Figure 3; Table 2, dates 9–25). The lower boundary of this phase marks the end of the occupational interruption and, as discussed above, is based on dates on lakebed sediment, a potsherd from burial fill, and the oldest burial in the occupation phase (Figures 3, 5A–C). The oldest skeletons within this phase have variegated or dark-stained bone and appear to have undergone episodes of inundation postdating their internment (Figure 5A–C, Table 2, dates 9–13). Occupational phase 3 at Gobero comes to a close with the youngest dated burial, a subadult approximately 11 years old (Figures 3, 5D; Table 2, date 25, 2910–2760 B.C.E., midpoint 2835 B.C.E.).

Phase 3 humans have more gracile skeletons and shorter stature for both males and females. They are buried most commonly in semi-flexed postures on either left or right sides (Figure 5D, E). Their crania are long, high and narrow, and their faces are taller with considerable alveolar prognathism (Figure 5C). Principal components analysis of craniometric data clearly distinguishes the mid-Holocene population at Gobero (Gob-m) from all other sampled populations, including the early Holocene population at Gobero, Iberomaurusian and Capsian populations from the Maghreb, “Mechtoids” from Mali and Mauritania, as well as much older Aterian samples (Figure 6). The morphological isolation of the mid-Holocene population from Gobero is particularly noteworthy, as several of the other populations sampled (WMC, Mali, Maur) are believed to be mid-Holocene contemporaries.

Grave goods occur in approximately 20% of the burials excavated thus far (7 of 35 burials) and include bones or tusks from wild fauna, ceramics, lithic projectile points, and bone, ivory and shell ornaments (Figures 5B, 7A, B, H, K–M). Although the disc knife that characterizes the mid-Holocene Tenerean industry [28], [29] has never been recovered in situ, small projectile points that also characterize the Tenerean tool kit are present in some burials that are directly dated to the mid-Holocene (Figure 7H; Table 2, date 20, 3500–3130 B.C.E., midpoint 3315 B.C.E.). Burials of particular note include an adult male with his skull resting on a half vessel decorated with an alternately pivoting stamped impression (Figure 7A, B; Table 2, date 18, midpoint 3500 B.C.E). Another adult male was buried in a recumbent pose seated on the carapace of a mud turtle (Figure 5A–C; Table 2, dates 9, 10, midpoint average 4635 B.C.E.). A triple burial, composed of an adult female and two juveniles, has intertwined arms, hands and legs, suggesting that they died nearly simultaneously and were interred in an intimate pose within a short period of time (Figure 5E, F; Table 2, date 20, midpoint 3315 B.C.E). Four hollow-based points lie between their limbs and underneath their skeletons (Figure 7H), and pollen clusters from flower heads of the wool flower (Celosia) were detected in underlying sediment. Like other burials at Gobero, these individuals show no sign of a violent traumatic death.

A conspicuous fine-grained green rock (with tan and brown variants) was often used for points, scrapers and adzes (Figure 7G, I) and always used for the delicate Tenerean disc knives [28], [29] at sites east and south of the Aïr massif. Previously this distinctive rock was identified as microcrystalline quartz, initially as jasper [32] and later as silicified vitric tuff [28]. For some 50 years, its source has remained a matter of speculation. Along with amazonite, the green rock was cited as evidence of trade over distances of one thousand kilometers or more, in order to link the Aïr with Tibesti (northern Chad-southern Libya) or regions farther afield [28], [33], [34].

Thin sections of artifacts made from the green rock and its color variants show the near absence of quartz. It is correctly identified as a felsite, a fine-grained volcanic rock composed of microcrystalline feldspar [35]. During reconnaissance a short distance (160 km) north of Gobero on the edge of the Aïr massif, we located a narrow outcrop of green felsite rock near the Alallaka wadi (Figures 1A, 8A). The site is littered with debitage from a longstanding knapping operation (Figure 8B). The frequent use of this rock at Gobero and Adrar Bous and its availability in nearby wadis along the eastern edge of the massif (Takolokouzet highland) suggests there were multiple felsite sources local to the Aïr. Given the absence of thorough geologic reconnaissance in the Aïr or any comparative trace element analysis, neither felsite nor amazonite provides evidence to infer trans-Saharan trade in the early or mid-Holocene.

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

(A)-An intrusion of green microcrystalline feldpar, or felsite [35], 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.

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At least semi-sedentary occupation is inferred from the number and density of undisturbed mid-Holocene burials, lack of evidence from strontium isotope analysis for enhanced mobility, abundance of lithic debitage on site, presence of groundstones, and numerous rodent marks on human bone and ornaments indicative of commensal species (Figure 7L) [36], [37]. The prevalence of juveniles of very young age among the interred also favors longer term occupation by family groups over transient visitation of the area as a watering hole or attractive hunting ground.

Clams (Mutela), small catfish (Clarias) and tilapia dominate the midden fauna (Figure 9), which also includes bones and teeth from hippos, a small antelope, small carnivores, softshell turtles and crocodiles (Table 5; middens 1–4). Domesticated cattle (Bos taurus) are present but unlike Adrar Bous [28], [29] comprise only a minor component of the midden and area fauna (Figure 3, Bos partial mandible on chart sidebar; GF10). The scarcity of bones or teeth of domesticated cattle suggests a subsistence economy emphasizing fishing in shallow waters and hunting of a range of savanna vertebrates. The gathering of grain and cattle pastoralism may also have played important nutritional or economic roles; further data relevant to occupancy and subsistence patterns are needed, such as seasonality data from piscine otoliths recovered from middens. Elsewhere in the southern Sahara, diversification of dietary resources that combine gathering, hunting, fishing and pastoralism seems to occur under less certain climatic conditions [34], [38], [39], a pattern that may well accommodate the emerging archaeological record during the mid-Holocene at Gobero.

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.).

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Pollen spectra from phase 3 burials indicate a mosaic of habitats. Open savannas with shrubland and grassland vegetation dominated, with sporadic presence of a fairly diversified Sudanian and tropical tree flora (Figure 10). Plants linked to wet environments include hydrophytes, which indicate the presence of shallow freshwater lakes. Xeric and psammophilous plants indicate the presence of sandy soils.