Nick Barton

82,000-year-old shell beads from North Africa and implications for the origins of modern human behavior

The first appearance of explicitly symbolic objects in the archaeological record marks a fundamental stage in the emergence of modern social behavior in Homo. Ornaments such as shell beads represent some of the earliest objects of this kind. We report on examples of perforated Nassarius gibbosulus shell beads from Grotte des Pigeons (Taforalt, Morocco), North Africa. These marine shells come from archaeological levels dated by luminescence and uranium-series techniques to ≈82,000 years ago. They confirm evidence of similar ornaments from other less well dated sites in North Africa and adjacent areas of southwest Asia. The shells are of the same genus as shell beads from slightly younger levels at Blombos Cave in South Africa. Wear patterns on the shells imply that some of them were suspended, and, as at Blombos, they were covered in red ochre. These findings imply an early distribution of bead-making in Africa and southwest Asia at least 40 millennia before the appearance of similar cultural manifestations in Europe.

Additional evidence on the use of personal ornaments in the Middle Paleolithic of North Africa

Recent investigations into the origins of symbolism indicate that personal ornaments in the form of perforated marine shell beads were used in the Near East, North Africa, and SubSaharan Africa at least 35 ka earlier than any personal ornaments in Europe. Together with instances of pigment use, engravings, and formal bone tools, personal ornaments are used to support an early emergence of behavioral modernity in Africa, associated with the origin of our species and significantly predating the timing for its dispersal out of Africa. Criticisms have been leveled at the low numbers of recovered shells, the lack of secure dating evidence, and the fact that documented examples were not deliberately shaped. In this paper, we report on 25 additional shell beads from four Moroccan Middle Paleolithic sites. We review their stratigraphic and chronological contexts and address the issue of these shells having been deliberately modified and used. We detail the results of comparative analyses of modern, fossil, and archaeological assemblages and microscopic examinations of the Moroccan material. We conclude that Nassarius shells were consistently used for personal ornamentation in this region at the end of the last interglacial. Absence of ornaments at Middle Paleolithic sites postdating Marine Isotope Stage 5 raises the question of the possible role of climatic changes in the disappearance of this hallmark of symbolic behavior before its reinvention 40 ka ago. Our results suggest that further inquiry is necessary into the mechanisms of cultural transmission within early Homo sapiens populations.

Volcanic ash layers illuminate the resilience of Neanderthals and early modern humans to natural hazards

Marked changes in human dispersal and development during the Middle to Upper Paleolithic transition have been attributed to massive volcanic eruption and/or severe climatic deterioration. We test this concept using records of volcanic ash layers of the Campanian Ignimbrite eruption dated to ca. 40,000 y ago (40 ka B.P.). The distribution of the Campanian Ignimbrite has been enhanced by the discovery of cryptotephra deposits (volcanic ash layers that are not visible to the naked eye) in archaeological cave sequences. They enable us to synchronize archaeological and paleoclimatic records through the period of transition from Neanderthal to the earliest anatomically modern human populations in Europe. Our results confirm that the combined effects of a major volcanic eruption and severe climatic cooling failed to have lasting impacts on Neanderthals or early modern humans in Europe. We infer that modern humans proved a greater competitive threat to indigenous populations than natural disasters.

Earliest evidence for caries and exploitation of starchy plant foods in Pleistocene hunter-gatherers from Morocco

Significance We present early evidence linking a high prevalence of caries to a reliance on highly cariogenic wild plant foods in Pleistocene hunter-gatherers from North Africa. This evidence predates other high caries populations and the first signs of food production by several thousand years. We infer that increased reliance on wild plants rich in fermentable carbohydrates caused an early shift toward a disease-associated oral microbiota. Systematic harvesting and processing of wild food resources supported a more sedentary lifestyle during the Iberomaurusian than previously recognized. This research challenges commonly held assumptions that high rates of caries are indicative of agricultural societies. Dental caries is an infectious disease that causes tooth decay. The high prevalence of dental caries in recent humans is attributed to more frequent consumption of plant foods rich in fermentable carbohydrates in food-producing societies. The transition from hunting and gathering to food production is associated with a change in the composition of the oral microbiota and broadly coincides with the estimated timing of a demographic expansion in Streptococcus mutans, a causative agent of human dental caries. Here we present evidence linking a high prevalence of caries to reliance on highly cariogenic wild plant foods in Pleistocene hunter-gatherers from North Africa, predating other high caries populations and the first signs of food production by several thousand years. Archaeological deposits at Grotte des Pigeons in Morocco document extensive evidence for human occupation during the Middle Stone Age and Later Stone Age (Iberomaurusian), and incorporate numerous human burials representing the earliest known cemetery in the Maghreb. Macrobotanical remains from occupational deposits dated between 15,000 and 13,700 cal B.P. provide evidence for systematic harvesting and processing of edible wild plants, including acorns and pine nuts. Analysis of oral pathology reveals an exceptionally high prevalence of caries (51.2% of teeth in adult dentitions), comparable to modern industrialized populations with a diet high in refined sugars and processed cereals. We infer that increased reliance on wild plants rich in fermentable carbohydrates and changes in food processing caused an early shift toward a disease-associated oral microbiota in this population.

Were Rivers Flowing across the Sahara During the Last Interglacial? Implications for Human Migration through Africa

Human migration north through Africa is contentious. This paper uses a novel palaeohydrological and hydraulic modelling approach to test the hypothesis that under wetter climates c.100,000 years ago major river systems ran north across the Sahara to the Mediterranean, creating viable migration routes. We confirm that three of these now buried palaeo river systems could have been active at the key time of human migration across the Sahara. Unexpectedly, it is the most western of these three rivers, the Irharhar river, that represents the most likely route for human migration. The Irharhar river flows directly south to north, uniquely linking the mountain areas experiencing monsoon climates at these times to temperate Mediterranean environments where food and resources would have been abundant. The findings have major implications for our understanding of how humans migrated north through Africa, for the first time providing a quantitative perspective on the probabilities that these routes were viable for human habitation at these times.

Human Burial Evidence from Hattab II Cave and the Question of Continuity in Late Pleistocene–Holocene Mortuary Practices in Northwest Africa

Archaeological excavations in 2002-3 at Hattab H Cave in northwestern Morocco revealed all undisturbed Late Palaeolithic Iberomaurusian human burial. This is the first Iberomaurusian inhumation discovered in the region. The skeleton is probably that Of a male aged between 25 and 30 years. The individual shows a characteristic absence of the central upper incisors reported in other Iberomaurusian burials. Accompanying the burial are a stone core and a number of grave goods including bone points, a marine gastropod and a gazelle horn core. Thermoluminescence dating of a burnt stone artefact in association with the burial has provided an age of 8900 +/- 1100 BP. This is one of the youngest ages reported for the Iberomaurusian and raises questions about persistence of hunter-gatherer societies in the Maghreb and the potential for continuity in burial practices with the earliest Neolithic.

Iberomaurusian funerary behaviour: evidence from Grotte des Pigeons, Taforalt, Morocco.

Grotte des Pigeons at Taforalt, north-east Morocco, is well known for a large assemblage of Iberomaurusian (Epipalaeolithic) skeletons, possibly representing the earliest and most extensively used prehistoric cemetery in North Africa. New archaeological excavations carried out in 2005 and 2006 revealed further human remains in a largely undisturbed burial area in an alcove at the back of the cave. This discovery provides the first opportunity to report on Iberomaurusian human mortuary activity at this site. Reported here are a closely spaced and inter-cutting series of four burials. These contained the remains of four adults, of which three were buried in a seated or slightly reclining position facing towards the cave entrance and one was buried in a highly flexed position on its left side. The distribution of articulated and disarticulated bones suggested intensive use of the area, with earlier burials disturbed or truncated by subsequent burials, and displaced skeletal elements deliberately or unwittingly incorporated into later depositions. Through this process, parts of a single skeleton were redistributed among several discrete graves and within the surrounding deposit. Some aspects of the Iberomaurusian funerary tradition that are evident from the human remains excavated in the 1950s are absent in the newly excavated adult burials, suggesting a possible elaboration of funerary activity over time.

North African Origins of Symbolically Mediated Behaviour and the Aterian

Abstract The appearance of personal ornaments in the Middle Palaeolithic/Middle Stone Age of North Africa has been widely recognised as indicating that archaic modern humans in this region had developed sophisticated ways of sharing, storing and transmitting coded information within and across groups. In this paper we discuss whether the first appearance of explicitly symbolic objects such as Nassarius shell beads in North Africa reflected a stage of rapid acceleration in cultural change across this region. A related issue concerns the question of what if any external factors may have given rise to innovations in technology and symbolic material culture and, finally, why these developments may have lacked longevity and ended in cultural loss as they probably also did in other parts of Africa.

Range shifts or extinction? : Ancient DNA and distribution modelling reveal past and future responses to climate warming in cold-adapted birds

Global warming is predicted to cause substantial habitat rearrangements, with the most severe effects expected to occur in high-latitude biomes. However, one major uncertainty is whether species will be able to shift their ranges to keep pace with climate-driven environmental changes. Many recent studies on mammals have shown that past range contractions have been associated with local extinctions rather than survival by habitat tracking. Here, we have used an interdisciplinary approach that combines ancient DNA techniques, coalescent simulations and species distribution modelling, to investigate how two common cold-adapted bird species, willow and rock ptarmigan (Lagopus lagopus and Lagopus muta), respond to long-term climate warming. Contrary to previous findings in mammals, we demonstrate a genetic continuity in Europe over the last 20 millennia. Results from back-casted species distribution models suggest that this continuity may have been facilitated by uninterrupted habitat availability and potentially also the greater dispersal ability of birds. However, our predictions show that in the near future, some isolated regions will have little suitable habitat left, implying a future decrease in local populations at a scale unprecedented since the last glacial maximum.

Pleistocene North African genomes link Near Eastern and sub-Saharan African human populations

Relationships among North Africans The general view is that Eurasians mostly descend from a single group of humans that dispersed outside of sub-Saharan Africa around 50,000 to 100,000 years ago. Present-day North Africans share a majority of their ancestry with present-day Near Easterners, but not with sub-Saharan Africans. To investigate this conundrum, Van de Loosdrecht et al. sequenced high-quality DNA obtained from bone samples of seven individuals from Taforalt in eastern Morocco dating from the Later Stone Age, about 15,000 years ago. The Taforalt individuals were found to be most closely related to populations from the Near East (Natufians), with a third of their ancestry from sub-Saharan Africa. No evidence was found for introgression with western Europeans, despite attribution to the Iberomaurusian culture. None of the present-day or ancient Holocene African groups are a good proxy for the sub-Saharan genetic component. Science, this issue p. 548 Ancient human genomes suggest dynamic interactions among Pleistocene African populations. North Africa is a key region for understanding human history, but the genetic history of its people is largely unknown. We present genomic data from seven 15,000-year-old modern humans, attributed to the Iberomaurusian culture, from Morocco. We find a genetic affinity with early Holocene Near Easterners, best represented by Levantine Natufians, suggesting a pre-agricultural connection between Africa and the Near East. We do not find evidence for gene flow from Paleolithic Europeans to Late Pleistocene North Africans. The Taforalt individuals derive one-third of their ancestry from sub-Saharan Africans, best approximated by a mixture of genetic components preserved in present-day West and East Africans. Thus, we provide direct evidence for genetic interactions between modern humans across Africa and Eurasia in the Pleistocene.