Michael D. Petraglia

The Prehistory of the Arabian Peninsula: Deserts, Dispersals, and Demography

As a geographic connection between Africa and the rest of Eurasia, the Arabian Peninsula occupies a central position in elucidating hominin evolution and dispersals. Arabia has been characterized by extreme environmental fluctuation in the Quaternary, with profound evolutionary and demographic consequences. Despite the importance of the region, Arabia remains understudied. Recent years, however, have seen major developments in environmental studies and archeology, revealing that the region contains important records that should play a significant role in future paleoanthropological narratives. 1–3 The emerging picture of Arabia suggests that numerous dispersals of hominin populations into the region occurred. Populations subsequently followed autochthonous trajectories, creating a distinctive regional archeological record. Debates continue on the respective roles of regional hominin extinctions and population continuity, with the latter suggesting adaptation to arid conditions.

Ecological consequences of human niche construction: Examining long-term anthropogenic shaping of global species distributions

The exhibition of increasingly intensive and complex niche construction behaviors through time is a key feature of human evolution, culminating in the advanced capacity for ecosystem engineering exhibited by Homo sapiens. A crucial outcome of such behaviors has been the dramatic reshaping of the global biosphere, a transformation whose early origins are increasingly apparent from cumulative archaeological and paleoecological datasets. Such data suggest that, by the Late Pleistocene, humans had begun to engage in activities that have led to alterations in the distributions of a vast array of species across most, if not all, taxonomic groups. Changes to biodiversity have included extinctions, extirpations, and shifts in species composition, diversity, and community structure. We outline key examples of these changes, highlighting findings from the study of new datasets, like ancient DNA (aDNA), stable isotopes, and microfossils, as well as the application of new statistical and computational methods to datasets that have accumulated significantly in recent decades. We focus on four major phases that witnessed broad anthropogenic alterations to biodiversity—the Late Pleistocene global human expansion, the Neolithic spread of agriculture, the era of island colonization, and the emergence of early urbanized societies and commercial networks. Archaeological evidence documents millennia of anthropogenic transformations that have created novel ecosystems around the world. This record has implications for ecological and evolutionary research, conservation strategies, and the maintenance of ecosystem services, pointing to a significant need for broader cross-disciplinary engagement between archaeology and the biological and environmental sciences.

Out of Africa: New hypotheses and evidence for the dispersal of Homo sapiens along the Indian Ocean rim

Abstract The dispersal of Homo sapiens out of Africa is a significant topic in human evolutionary studies. Most investigators agree that our species arose in Africa and subsequently spread out to occupy much of Eurasia. Researchers have argued that populations expanded along the Indian Ocean rim at ca 60 000 years ago during a single rapid dispersal event, probably employing a coastal route towards Australasia. Archaeologists have been relatively silent about the movement and expansion of human populations in terrestrial environments along the Indian Ocean rim, although it is clear that Homo sapiens reached Australia by ca 45 000 years ago. Here, we synthesize and document current genetic and archaeological evidence from two major landmasses, the Arabian peninsula and the Indian subcontinent, regions that have been underplayed in the story of out of Africa dispersals. We suggest that modern humans were present in Arabia and South Asia earlier than currently believed, and probably coincident with the presence of Homo sapiens in the Levant between ca 130 and 70 000 years ago. We show that climatic and environmental fluctuations during the Late Pleistocene would have had significant demographic effects on Arabian and South Asian populations, though indigenous populations would have responded in different ways. Based on a review of the current genetic, archaeological and environmental data, we indicate that demographic patterns in Arabia and South Asia are more interesting and complex than surmised to date.

The Middle Palaeolithic of Arabia: Implications for modern human origins, behaviour and dispersals

The Middle Palaeolithic record of the Arabian Peninsula can provide crucial evidence for understanding human dispersal. The authors summarise the archaeological evidence and suggest some of the routes taken by the earliest humans coming out of Africa, including one implying the use of boats. Early populations adapted to a hospitable environment, but had later to adapt to the advance of the desert.

The Lower Paleolithic of the Arabian Peninsula: Occupations, Adaptations, and Dispersals

To understand major processes of human evolution during the Plio- Pleistocene, it is necessary to consider the available evidence from key regions of the Old World. The Arabian peninsula is often depicted as a key geographic route for hominin dispersals in “Out of Africa” models, although the available primary evidence is rarely cited. And yet, significant Lower Paleolithic assemblages have been identified in many parts of the peninsula, including in areas near the Strait of Bab al Mandab. The presence of Oldowan-like and Acheulean assemblages may reflect at least two major dispersals outside of Africa. Acheulean localities are particularly abundant on the Arabian peninsula, and variations in stone tool manufacturing techniques and tool-type frequencies may reflect temporal changes in assemblages. Although there is good potential to chronometrically date sites in the Arabian peninsula, absolute dating methods have not been adequately applied, most temporal reconstructions relying on typotechnological change. If the Arabian peninsula is to provide solid evidence for understanding hominin adaptation and dispersal patterns, future fieldwork in secure depositional contexts needs to be conducted to overcome current limits in dating and environmental reconstructions.

Genomic analyses inform on migration events during the peopling of Eurasia

High-coverage whole-genome sequence studies have so far focused on a limited number of geographically restricted populations, or been targeted at specific diseases, such as cancer. Nevertheless, the availability of high-resolution genomic data has led to the development of new methodologies for inferring population history and refuelled the debate on the mutation rate in humans. Here we present the Estonian Biocentre Human Genome Diversity Panel (EGDP), a dataset of 483 high-coverage human genomes from 148 populations worldwide, including 379 new genomes from 125 populations, which we group into diversity and selection sets. We analyse this dataset to refine estimates of continent-wide patterns of heterozygosity, long- and short-distance gene flow, archaic admixture, and changes in effective population size through time as well as for signals of positive or balancing selection. We find a genetic signature in present-day Papuans that suggests that at least 2% of their genome originates from an early and largely extinct expansion of anatomically modern humans (AMHs) out of Africa. Together with evidence from the western Asian fossil record, and admixture between AMHs and Neanderthals predating the main Eurasian expansion, our results contribute to the mounting evidence for the presence of AMHs out of Africa earlier than 75,000 years ago.

Rethinking the dispersal of Homo sapiens out of Africa.

Current fossil, genetic, and archeological data indicate that Homo sapiens originated in Africa in the late Middle Pleistocene. By the end of the Late Pleistocene, our species was distributed across every continent except Antarctica, setting the foundations for the subsequent demographic and cultural changes of the Holocene. The intervening processes remain intensely debated and a key theme in hominin evolutionary studies. We review archeological, fossil, environmental, and genetic data to evaluate the current state of knowledge on the dispersal of Homo sapiens out of Africa. The emerging picture of the dispersal process suggests dynamic behavioral variability, complex interactions between populations, and an intricate genetic and cultural legacy. This evolutionary and historical complexity challenges simple narratives and suggests that hybrid models and the testing of explicit hypotheses are required to understand the expansion of Homo sapiens into Eurasia.

Population increase and environmental deterioration correspond with microlithic innovations in South Asia ca. 35,000 years ago

Genetic studies of South Asias population history have led to postulations of a significant and early population expansion in the subcontinent, dating to sometime in the Late Pleistocene. We evaluate this argument, based on new mtDNA analyses, and find evidence for significant demographic transition in the subcontinent, dating to 35–28 ka. We then examine the paleoenvironmental and, particularly, archaeological records for this time period and note that this putative demographic event coincides with a period of ecological and technological change in South Asia. We document the development of a new diminutive stone blade (microlithic) technology beginning at 35–30 ka, the first time that the precocity of this transition has been recognized across the subcontinent. We argue that the transition to microlithic technology may relate to changes in subsistence practices, as increasingly large and probably fragmented populations exploited resources in contracting favorable ecological zones just before the onset of full glacial conditions.

The oldest and longest enduring microlithic sequence in India: 35 000 years of modern human occupation and change at the Jwalapuram Locality 9 rockshelter

Abstract The Jwalapuram Locality 9 rockshelter in southern India dates back to 35 000 years ago and it is emerging as one of the key sites for documenting human activity and behaviour in South Asia. The excavated assemblage includes a proliferation of lithic artefacts, beads, worked bone and fragments of a human cranium. The industry is microlithic in character, establishing Jwalapuram 9 as one of the oldest and most important sites of its kind in South Asia.

Hominin dispersal into the Nefud Desert and Middle palaeolithic settlement along the Jubbah Palaeolake, Northern Arabia.

The Arabian Peninsula is a key region for understanding hominin dispersals and the effect of climate change on prehistoric demography, although little information on these topics is presently available owing to the poor preservation of archaeological sites in this desert environment. Here, we describe the discovery of three stratified and buried archaeological sites in the Nefud Desert, which includes the oldest dated occupation for the region. The stone tool assemblages are identified as a Middle Palaeolithic industry that includes Levallois manufacturing methods and the production of tools on flakes. Hominin occupations correspond with humid periods, particularly Marine Isotope Stages 7 and 5 of the Late Pleistocene. The Middle Palaeolithic occupations were situated along the Jubbah palaeolake-shores, in a grassland setting with some trees. Populations procured different raw materials across the lake region to manufacture stone tools, using the implements to process plants and animals. To reach the Jubbah palaeolake, Middle Palaeolithic populations travelled into the ameliorated Nefud Desert interior, possibly gaining access from multiple directions, either using routes from the north and west (the Levant and the Sinai), the north (the Mesopotamian plains and the Euphrates basin), or the east (the Persian Gulf). The Jubbah stone tool assemblages have their own suite of technological characters, but have types reminiscent of both African Middle Stone Age and Levantine Middle Palaeolithic industries. Comparative inter-regional analysis of core technology indicates morphological similarities with the Levantine Tabun C assemblage, associated with human fossils controversially identified as either Neanderthals or Homo sapiens.