Neural networks differentiate between Middle and Later Stone age lithic assemblages in eastern Africa

The Middle to Later Stone Age transition marks a major change in how Late Pleistocene African populations produced and used stone tool kits, but is manifest in various ways, places and times across the continent. Alongside changing patterns of raw material use and decreasing artefact sizes, changes in artefact types are commonly employed to differentiate Middle Stone Age (MSA) and Later Stone Age (LSA) assemblages. The current paper employs a quantitative analytical framework based upon the use of neural networks to examine changing constellations of technologies between MSA and LSA assemblages from eastern Africa. Network ensembles were trained to differentiate LSA assemblages from Marine Isotope Stage 3&4 MSA and Marine Isotope Stage 5 MSA assemblages based upon the presence or absence of 16 technologies. Simulations were used to extract significant indicator and contra-indicator technologies for each assemblage class. The trained network ensembles classified over 94% of assemblages correctly, and identified 7 key technologies that significantly distinguish between assemblage classes. These results clarify both temporal changes within the MSA and differences between MSA and LSA assemblages in eastern Africa

Ecological drivers of hunter-gatherer lithic technology from the Middle and Later Stone Age in Central Africa

Central Africa is a key region for examining patterns of hunter-gatherer inhabitation and engagement with ecological diversity and environmental change. In contrast to adjacent regions, however, the archaeological record of prehistoric hunter-gatherer populations in Central Africa is underrepresented in studies of recent human evolution. This limited engagement with Central African archaeological records in part stems from the complexities of identifying, excavating, and dating hunter-gatherer sites in what are today often heavily forested environments, a focus on named stone tool industries from undated sites to structure the record, and highly limited means to associate dated hunter-gatherer occupations with proxy records of environmental conditions. Here, we present a novel synthesis of prehistoric hunter-gatherer stone tool assemblages from dated Central African sites and use climate model datasets to illuminate the environmental and ecological landscapes in which they were deployed. Our results suggest a significant ecological shift occurred from 14,000 years ago onwards, associated with a greater engagement with broadleaf forests. We examine the extent to which a range of geographic and paleoclimatic drivers can explain patterns of gross assemblage composition and the appearance of individual lithic technologies highlighting the significant role of changes in altitude, precipitation, seasonality, and ecology. Notably, considerable continuity can be observed between the habitat ranges of contemporary hunter-gatherer populations in Central Africa and prehistoric occupations that significantly precede the appearance of farming lifeways in the region

Evaluating refugia in recent human evolution in Africa

Homo sapiens have adapted to an incredible diversity of habitats around the globe. This capacity to adapt to different landscapes is clearly expressed within Africa, with Late Pleistocene Homo sapiens populations occupying savannahs, woodlands, coastlines and mountainous terrain. As the only area of the world where Homo sapiens have clearly persisted through multiple glacial-interglacial cycles, Africa is the only continent where classic refugia models can be formulated and tested to examine and describe changing patterns of past distributions and human phylogeographies. The potential role of refugia has frequently been acknowledged in the Late Pleistocene palaeoanthropological literature, yet explicit identification of potential refugia has been limited by the patchy nature of palaeoenvironmental and archaeological records, and the low temporal resolution of climate or ecological models. Here, we apply potential climatic thresholds on human habitation, rooted in ethnographic studies, in combination with high-resolution model datasets for precipitation and biome distributions to identify persistent refugia spanning the Late Pleistocene (130–10 ka). We present two alternate models suggesting that between 27% and 66% of Africa may have provided refugia to Late Pleistocene human populations, and examine variability in precipitation, biome and ecotone distributions within these refugial zones. This article is part of the theme issue ‘Tropical forests in the deep human past’

A spatiotemporally explicit paleoenvironmental framework for the Middle Stone Age of eastern Africa.

Eastern Africa has played a prominent role in debates about human evolution and dispersal due to the presence of rich archaeological, palaeoanthropological and palaeoenvironmental records. However, substantial disconnects occur between the spatial and temporal resolutions of these data that complicate their integration. Here, we apply high-resolution climatic simulations of two key parameters, mean annual temperature and precipitation, and a biome model, to produce a highly refined characterisation of the environments inhabited during the eastern African Middle Stone Age. Occupations are typically found in sub-humid climates and landscapes dominated by or including tropical xerophytic shrubland. Marked expansions from these core landscapes include movement into hotter, low-altitude landscapes in Marine Isotope Stage 5 and cooler, high-altitude landscapes in Marine Isotope Stage 3, with the recurrent inhabitation of ecotones between open and forested habitats. Through our use of high-resolution climate models, we demonstrate a significant independent relationship between past precipitation and patterns of Middle Stone Age stone tool production modes overlooked by previous studies. Engagement with these models not only enables spatiotemporally explicit examination of climatic variability across Middle Stone Age occupations in eastern Africa but enables clearer characterisation of the habitats early human populations were adapted to, and how they changed through time

A spatiotemporally explicit paleoenvironmental framework for the Middle Stone Age of eastern Africa.

Eastern Africa has played a prominent role in debates about human evolution and dispersal due to the presence of rich archaeological, palaeoanthropological and palaeoenvironmental records. However, substantial disconnects occur between the spatial and temporal resolutions of these data that complicate their integration. Here, we apply high-resolution climatic simulations of two key parameters, mean annual temperature and precipitation, and a biome model, to produce a highly refined characterisation of the environments inhabited during the eastern African Middle Stone Age. Occupations are typically found in sub-humid climates and landscapes dominated by or including tropical xerophytic shrubland. Marked expansions from these core landscapes include movement into hotter, low-altitude landscapes in Marine Isotope Stage 5 and cooler, high-altitude landscapes in Marine Isotope Stage 3, with the recurrent inhabitation of ecotones between open and forested habitats. Through our use of high-resolution climate models, we demonstrate a significant independent relationship between past precipitation and patterns of Middle Stone Age stone tool production modes overlooked by previous studies. Engagement with these models not only enables spatiotemporally explicit examination of climatic variability across Middle Stone Age occupations in eastern Africa but enables clearer characterisation of the habitats early human populations were adapted to, and how they changed through time

Rethinking human responses to sea-level rise : the Mesolithic occupation of the Channel Islands

This work provides new insights into human responses to and perceptions of sea-level rise at a time when the landscapes of north-west Europe were radically changing. These issues are investigated through a case study focused on the Channel Islands. We report on the excavation of two sites, Canal du Squez in Jersey and Lihou (GU582) in Guernsey, and the study of museum collections across the Channel Islands. We argue that people were drawn to this area as a result of the dynamic environmental processes occurring and the opportunities these created. The evidence suggests that the area was a particular focus during the Middle Mesolithic, when Guernsey and Alderney were already islands and while Jersey was a peninsula of northern France. Insularisation does not appear to have created a barrier to occupation during either the Middle or Final Mesolithic, indicating the appearance of lifeways increasingly focused on maritime voyaging and marine resources from the second half of the 9th millennium BC onwards.PostprintPeer reviewe

Microliths in the South Asian rainforest ~45-4 ka: New insights from Fa-Hien Lena Cave, Sri Lanka

Microliths–small, retouched, often-backed stone tools–are often interpreted to be the product of composite tools, including projectile weapons, and efficient hunting strategies by modern humans. In Europe and Africa these lithic toolkits are linked to hunting of medium- and large-sized game found in grassland or woodland settings, or as adaptations to risky environments during periods of climatic change. Here, we report on a recently excavated lithic assemblage from the Late Pleistocene cave site of Fa-Hien Lena in the tropical evergreen rainforest of Sri Lanka. Our analyses demonstrate that Fa-Hien Lena represents the earliest microlith assemblage in South Asia (c. 48,000–45,000 cal. years BP) in firm association with evidence for the procurement of small to medium size arboreal prey and rainforest plants. Moreover, our data highlight that the lithic technology of Fa-Hien Lena changed little over the long span of human occupation (c. 48,000–45,000 cal. years BP to c. 4,000 cal. years BP) indicating a successful, stable technological adaptation to the tropics. We argue that microlith assemblages were an important part of the environmental plasticity that enabled Homo sapiens to colonise and specialise in a diversity of ecological settings during its expansion within and beyond Africa. The proliferation of diverse microlithic technologies across Eurasia c. 48–45 ka was part of a flexible human ‘toolkit’ that assisted our species’ spread into all of the world’s environments, and the development of specialised technological and cultural approaches to novel ecological situations

Late Pleistocene to early-Holocene rainforest foraging in Sri Lanka:Multidisciplinary analysis at Kitulgala Beli-lena

Sri Lanka has produced the earliest clear evidence for Homo sapiens fossils in South Asia and research in the region has provided important insights into modern human adaptations and cultural practices during the last ca. 45,000 years. However, in-depth multidisciplinary analyses of Late Pleistocene and Holocene sequences remain limited to just two sites, Fa Hien-lena and Batadomba-lena. Here, we present our findings from the reinvestigation of a third site, Kitulgala Beli-lena. New chronometric dating from the site confirms the presence of humans as early as ca. 45,000 cal. BP. in the island's Wet Zone rainforest region. Our analyses of macrobotanical, molluscan, and vertebrate remains from the rockshelter show that this early human presence is associated with rainforest foraging. The Late Pleistocene deposits yielded evidence of wild breadfruit and kekuna nut extraction while the Holocene layers reveal a heavy reliance on semi-arboreal and arboreal small mammals as well as freshwater snails as a protein source. The lithic and osseous artefacts demonstrate that populations developed a sophisticated tool kit for the exploitation of their immediate landscapes. We place the rich Kitulgala Beli-lena dataset in its wider Sri Lankan context of Late Pleistocene foraging, as well as in wider discussions of our species’ adaptation to ‘extreme’ environments as it moved throughout Asia