Adaptive foraging behaviours in the Horn of Africa during Toba supereruption.

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.

A monumental cemetery built by eastern Africa's first herders near Lake Turkana, Kenya.

Monumental architecture is a prime indicator of social complexity, because it requires many people to build a conspicuous structure commemorating shared beliefs. Examining monumentality in different environmental and economic settings can reveal diverse reasons for people to form larger social units and express unity through architectural display. In multiple areas of Africa, monumentality developed as mobile herders created large cemeteries and practiced other forms of commemoration. The motives for such behavior in sparsely populated, unpredictable landscapes may differ from well-studied cases of monumentality in predictable environments with sedentary populations. Here we report excavations and ground-penetrating radar surveys at the earliest and most massive monumental site in eastern Africa. Lothagam North Pillar Site was a communal cemetery near Lake Turkana (northwest Kenya) constructed 5,000 years ago by eastern Africa's earliest pastoralists. Inside a platform ringed by boulders, a 119.5-m2 mortuary cavity accommodated an estimated minimum of 580 individuals. People of diverse ages and both sexes were buried, and ornaments accompanied most individuals. There is no evidence for social stratification. The uncertainties of living on a "moving frontier" of early herding-exacerbated by dramatic environmental shifts-may have spurred people to strengthen social networks that could provide information and assistance. Lothagam North Pillar Site would have served as both an arena for interaction and a tangible reminder of shared identity.

The bioarchaeology of mid-Holocene pastoralist cemeteries west of Lake Turkana, Kenya.

Early herders in eastern Africa built elaborate megalithic cemeteries ~ 5000 BP overlooking what is now Lake Turkana in northwestern Kenya. At least six 'pillar sites' were constructed during a time of rapid change: cattle, sheep, and goats were introduced to the basin as the lake was shrinking at the end of the African Humid Period. Cultural changes at this time include new lithic and ceramic technologies and the earliest monumentality in eastern Africa. Isolated human remains previously excavated from pillar sites east of Lake Turkana seemed to indicate that pillar site platforms were ossuaries for secondary burials. Recent bioarchaeological excavations at four pillar sites west of the lake have now yielded ≥49 individuals, most from primary and some from secondary interments, challenging earlier interpretations. Here we describe the mortuary cavities, and burial contexts, and included items such as adornments from Lothagam North, Lothagam West, Manemanya, and Kalokol pillar sites. In doing so, we reassess previous hypotheses regarding pillar site construction, use, and inter-site variability. We also present the first osteological analyses of skeletons buried at these sites. Although the human remains are fragmentary, they are nevertheless informative about the sex, age, and body size of the deceased and give evidence for health and disease processes. Periosteal moulds of long bone midshafts (n = 34 elements) suggest patterns of terrestrial mobility. Pillar site deposits provide important new insights into early herder lifeways in eastern Africa and the impact of the transition to pastoralism on past human populations.