Understanding Ancient Hominin Dispersals Using Artefactual Data: A Phylogeographic Analysis of Acheulean Handaxes

Background

Reconstructing the dispersal patterns of extinct hominins remains a challenging but essential goal. One means of supplementing fossil evidence is to utilize archaeological evidence in the form of stone tools. Based on broad dating patterns, it has long been thought that the appearance of Acheulean handaxe technologies outside of Africa was the result of hominin dispersals, yet independent tests of this hypothesis remain rare. Cultural transmission theory leads to a prediction of a strong African versus non-African phylogeographic pattern in handaxe datasets, if the African Acheulean hypothesis is to be supported.

Methodology/Principal Findings

Here, this prediction is tested using an intercontinental dataset of Acheulean handaxes and a biological phylogenetic method (maximum parsimony). The analyses produce a tree consistent with the phylogeographic prediction. Moreover, a bootstrap analysis provides evidence that this pattern is robust, and the maximum parsimony tree is also shown to be statistically different from a tree constrained by stone raw materials.

Conclusions/Significance

These results demonstrate that nested analyses of behavioural data, utilizing methods drawn from biology, have the potential to shed light on ancient hominin dispersals. This is an encouraging prospect for human palaeobiology since sample sizes for lithic artefacts are many orders of magnitude higher than those of fossil data. These analyses also suggest that the sustained occurrence of Acheulean handaxe technologies in regions such as Europe and the Indian subcontinent resulted from dispersals by African hominin populations.     

Human display and dispersal: A case study from biotidal Britain in the Middle and Upper Pleistocene

Hominin dispersal and human colonization have been hallmark concepts in the last two decades of palaeanthropological research, 1 - 7 even though the terminology in these approaches is loosely defined (Box 1). The number, frequency, and routes of dispersal have been analyzed on a global scale, 8 beginning with the earliest movement of hominins between Africa and Asia, and back again. 9 Investigating dispersals has provided a much‐needed dynamic to account for recent human origins in Africa 10 and the replacement elsewhere of older regional hominin populations that include the Neanderthals. 11 In the last twenty years, phylogeographies based on a wealth of molecular studies have added enormously to our understanding of global population history from the Paleolithic to the Vikings 12 and has, in particular, revitalized the study of farming dispersals. 13 As a result, Quaternary hominins and humans have been on the move as never before. However, not all of these movements are considered within an evolutionary framework. Interest has focused instead on using dispersals to support the claims for either a Neolithic or human revolution as the turning point in human prehistory. Here, I explore an alternative by considering the implications of the major shift that occurred in Paleolithic technology from instruments to containers. 14 I argue that this development can be explained by the selective pressure from population dispersal for novel forms of cultural display that enhanced information exchange among adaptive generalists and which allowed the stretching of social relationships in space and time. 15 The British Paleolithic record provides a case study.     

Multiple dispersals and modern human origins

Despite a massive endeavour, the problem of modern human origins not only remains unresolved, but is usually reduced to “Out of Africa” versus multiregional evolution. Not all would agree, but evidence for a single recent origin is accumulating. Here, we want to go beyond this debate and explore within the “Out of Africa” framework an issue that has not been fully addressed: the mechanism by which modern human diversity has developed. We believe there is no clear rubicon of modern Homo sapiens, and that multiple dispersals occurred from a morphologically variable population in Africa. Pre-existing African diversity is thus crucial to the way human diversity developed outside Africa. The pattern of diversity—behavioural, linguistic, morphological and genetic—can be interpreted as the result of dispersals, colonisation, differentiation and subsequent dispersals overlaid on former population ranges. The first dispersals would have originated in Africa from where two different geographical routes were possible, one through Ethiopia/Arabia towards South Asia, and one through North Africa/Middle East towards Eurasia.     

Dynamics of Green Sahara Periods and Their Role in Hominin Evolution

Astronomically forced insolation changes have driven monsoon dynamics and recurrent humid episodes in North Africa, resulting in green Sahara Periods (GSPs) with savannah expansion throughout most of the desert. Despite their potential for expanding the area of prime hominin habitats and favouring out-of-Africa dispersals, GSPs have not been incorporated into the narrative of hominin evolution due to poor knowledge of their timing, dynamics and landscape composition at evolutionary timescales. We present a compilation of continental and marine paleoenvironmental records from within and around North Africa, which enables identification of over 230 GSPs within the last 8 million years. By combining the main climatological determinants of woody cover in tropical Africa with paleoenvironmental and paleoclimatic data for representative (Holocene and Eemian) GSPs, we estimate precipitation regimes and habitat distributions during GSPs. Their chronology is consistent with the ages of Saharan archeological and fossil hominin sites. Each GSP took 2–3 kyr to develop, peaked over 4–8 kyr, biogeographically connected the African tropics to African and Eurasian mid latitudes, and ended within 2–3 kyr, which resulted in rapid habitat fragmentation. We argue that the well-dated succession of GSPs presented here may have played an important role in migration and evolution of hominins.     

A study of hominin dispersal out of Africa using computer simulations

A study of hominin dispersal out of Africa using computer simulations is presented. Attention is focused on the joint probability of the colonization of Western Europe later than 1 Ma and that of Eastern Asia prior to 1.6 or 1.8 Ma, as current archaeological estimates suggest. We found that the determinant factor to hominin dispersal is the mode of hominin movement. If the movement of all populations is uniform and their number great enough, greater than 300 in our models, then such movement favors the colonization of Eastern Asia and Western Europe at more or less the same time. On the other hand, the colonization acquires prominent probabilistic features if the number of populations migrating is small enough, smaller than 10 in our models, or when all hominin populations may move but there are only a few with much higher mobility. In this case, the joint probability for the earliest dispersals of hominins in Western Europe after 1 Ma and Eastern Asia prior to 1.6 Ma ranges from 0.02 to 0.05. The single probability of colonization of Western Europe after 1 Ma is very high, about 0.5 for the majority of the colonization routes, whereas the corresponding probability of the colonization of Eastern Asia prior to 1.6 Ma is ten times lower, about 0.05. The least probable event is the earliest colonization of Java prior to 1.6 Ma, to which our simulation attributes a probability of ca 0.01. Deserts, mountains, and mountain ranges may delay the arrival at a certain location; nevertheless, their effect on the joint probability is very small.     

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.     

Crossing the line: increasing body size in a trans-Wallacean lizard radiation (Cyrtodactylus,Gekkota)

The region between the Asian and Australian continental plates (Wallacea) demarcates the transition between two differentiated regional biotas. Despite this striking pattern, some terrestrial lineages have successfully traversed the marine barriers of Wallacea and subsequently diversified in newly colonized regions. The hypothesis that these dispersals between biogeographic realms are correlated with detectable shifts in evolutionary trajectory has however rarely been tested. Here, we analyse the evolution of body size in a widespread and exceptionally diverse group of gekkotan lizards (Cyrtodactylus), and show that a clade that has dispersed eastwards and radiated in the Australopapuan region appears to have significantly expanded its body size ‘envelope’ and repeatedly evolved gigantism. This pattern suggests that the biotic composition of the proto-Papuan Archipelago provided a permissive environment in which new colonists were released from evolutionary constraints operating to the west of Wallacea.     

Social intelligence, human intelligence and niche construction

This paper is about the evolution of hominin intelligence. I agree with defenders of the social intelligence hypothesis in thinking that externalist models of hominin intelligence are not plausible: such models cannot explain the unique cognition and cooperation explosion in our lineage, for changes in the external environment (e.g. increasing environmental unpredictability) affect many lineages. Both the social intelligence hypothesis and the social intelligence-ecological complexity hybrid I outline here are niche construction models. Hominin evolution is hominin response to selective environments that earlier hominins have made. In contrast to social intelligence models, I argue that hominins have both created and responded to a unique foraging mode; a mode that is both social in itself and which has further effects on hominin social environments. In contrast to some social intelligence models, on this view, hominin encounters with their ecological environments continue to have profound selective effects. However, though the ecological environment selects, it does not select on its own. Accidents and their consequences, differential success and failure, result from the combination of the ecological environment an agent faces and the social features that enhance some opportunities and suppress others and that exacerbate some dangers and lessen others. Individuals do not face the ecological filters on their environment alone, but with others, and with the technology, information and misinformation that their social world provides.     

Late Glacial Human Dispersals in Northern Europe and Disequilibrium Dynamics

There is mounting evidence for the non-analogue nature of Late Glacial (18,000–11,700 years BP) ecosystems. Several dispersal episodes of human forager groups moving into previously uninhabitable glacial or periglacial landscapes also occurred during this period. In palaearctic northern Europe, these dispersals are associated with a succession of archaeological technocomplexes that are traditionally thought to reflect changing adaptation strategies synchronised with contemporaneous environmental changes. Recent investigations into ecological disequilibrium dynamics suggest, however, that there may be a greater degree of mismatch between organisms and their environments, especially in arctic-type environments and during times of rapidly changing climate. We link these climatic changes to cultural changes via demographic inference. Based on recent dating evidence, environmental analyses and preliminary morphometric and technological analyses of lithic material, we infer that Late Glacial Palearctic foragers, similarly at disequilibrium and with very low population densities, were prone to regional extinction episodes. We focus in particular on ‘Hamburgian’ culture and its potentially failed dispersal into southern Scandinavia. In conclusion, we suggest avenues for further testing this hypothesis of regional extinction.     

Multiple cenozoic invasions of Africa by penguins (Aves, Sphenisciformes)

Africa hosts a single breeding species of penguin today, yet the fossil record indicates that a diverse array of now-extinct taxa once inhabited southern African coastlines. Here, we show that the African penguin fauna had a complex history involving multiple dispersals and extinctions. Phylogenetic analyses and biogeographic reconstructions incorporating new fossil material indicate that, contrary to previous hypotheses, the four Early Pliocene African penguin species do not represent an endemic radiation or direct ancestors of the living Spheniscus demersus (blackfooted penguin). A minimum of three dispersals to Africa, probably assisted by the eastward-flowing Antarctic Circumpolar and South Atlantic currents, occurred during the Late Cenozoic. As regional sea-level fall eliminated islands and reduced offshore breeding areas during the Pliocene, all but one penguin lineage ended in extinction, resulting in today's depleted fauna.     

Connecting local environmental sequences to global climate patterns: evidence from the hominin-bearing Hadar Formation, Ethiopia

Central to the debate surrounding global climate change and Plio-Pleistocene hominin evolution is the degree to which orbital-scale climate patterns influence low-latitude continental ecosystems and how these influences can be distinguished from regional volcano-tectonic events and local environmental effects. The Pliocene Hadar Formation of Ethiopia preserves a record of hominin paleoenvironments from roughly 3.5 to 2.2 Ma at a temporal resolution relevant to evolutionary change within hominins and other taxa. This study integrates the high-resolution sedimentological and paleontological records at Hadar with climate proxies such as marine core isotope, dust, and sapropel records. Consistent cycling observed both between and within fluvial and lacustrine depositional environments prior to 2.9 Ma at Hadar appears to be predominantly climatic in nature. In contrast a significant change in depositional facies after 2.9 Ma to sequences dominated by conglomerate cut-and-fill cycles indicates a strong tectonic signature related to regional developments in the Main Ethiopian Rift. While specific events seen in marine proxy records may have parallels in the Hadar environmental archive, their overall patterns of high versus low variability may be even more relevant. For example, periods of relatively high-amplitude climate oscillations between 3.15 and 2.95 Ma may be linked to noted size-related morphological changes within the Hadar Australopithecus afarensis lineage and a significant increase in more arid-adapted bovid taxa. Increased aridity in East Africa during this period is also indicated by peaks in eolian dust in the marine core record. Conversely, the dominant lacustrine phase at Hadar ca. 3.3 Ma coincides with the least variable period in several climate proxy records, including marine core foraminifera delta(18)O values and eolian dust concentration. This phase is also coeval with low insolation variability and a very distinct and significant long-term period of low dust percentage in circum-Africa marine cores.     

Geochronology of cave deposits at Liang Bua and of adjacent river terraces in the Wae Racang valley, western Flores, Indonesia: a synthesis of age estimates for the type locality of Homo floresiensis

A robust timeframe for the extant cave deposits at Liang Bua, and for the river terraces in the adjoining Wae Racang valley, is essential to constrain the period of existence and time of extinction of Homo floresiensis and other biota that have been excavated at this hominin type locality. Reliable age control is also required for the variety of artifacts excavated from these deposits, and to assist in environmental reconstructions for this river valley and for the region more broadly. In this paper, we summarize the available geochronological information for Liang Bua and its immediate environs, obtained using seven numerical-age methods: radiocarbon, thermoluminescence, optically- and infrared-stimulated luminescence (collectively known as optical dating), uranium-series, electron spin resonance, and coupled electron spin resonance/uranium-series. We synthesize the large number of numerical age determinations reported previously and present additional age estimates germane to questions of hominin evolution and extinction.     

Natural plant species inventory of hotspot areas in Arabian Peninsula: Southwest Al-Baha region,Saudi Arabia

Plant hotspot areas are the areas that are very rich in plant species diversity. These areas have a priority for conservation. To highlight the plant diversity for nature conservation purposes a case study in Al Baha region, Saudi Arabia is presented, in which the importance of the natural vegetation and flora of one of the hotspot areas of Saudi Arabia is evaluated through the explanation of its natural plant species. A survey study has been conducted in an area of 167.6 km2, a 97 sample each with 20X20 m were laid out covering the whole ecological zones of the study site. Data of flora, vegetation cover and topography were gathered from each sample site. The study revealed about 319 plant species belonging to 228 genera and 75 families. Two species were found endemic to Saudi Arabia, 14 were endemics to Arabian Peninsula, and five were regional endemics that are only found in East Africa and Arabian Peninsula, while 39 species are rare and endangered.     

Recent paleoanthropological excavations of in situ deposits at Makapansgat, South Africa--a first report

The Makapansgat Limeworks is a significant Pliocene site both for its sample of 35 hominin fossils as well as its wealth of fossil fauna. The lithological and paleontological successions reveal local environmental changes that are important for understanding the context of hominin evolution in southern Africa. Yet most of the site's fossils were found in dumps left behind by quarry operations, and the paleoecological interpretations rest upon debatable assumptions about the original fossil provenience. We have recently initiated systematic paleoanthropological excavations at Makapansgat to recover well provenanced fossils in order to: 1) assess whether faunal successions are discernable in the Makapansgat sequence; 2) assist environmental interpretations of the site; 3) and potentially recover the oldest hominins in South Africa, roughly coincident with Australopithecus afarensis in East Africa. This paper presents a summary of our current paleoenvironmental research at the Limeworks and preliminary results of ongoing in situ excavations.     

Early Human Speciation,Brain Expansion and Dispersal Influenced by African Climate Pulses

Early human evolution is characterised by pulsed speciation and dispersal events that cannot be explained fully by global or continental paleoclimate records. We propose that the collated record of ephemeral East African Rift System (EARS) lakes could be a proxy for the regional paleoclimate conditions experienced by early hominins. Here we show that the presence of these lakes is associated with low levels of dust deposition in both West African and Mediterranean records, but is not associated with long-term global cooling and aridification of East Africa. Hominin expansion and diversification seem to be associated with climate pulses characterized by the precession-forced appearance and disappearance of deep EARS lakes. The most profound period for hominin evolution occurs at about 1.9 Ma; with the highest recorded diversity of hominin species, the appearance of Homo (sensu stricto) and major dispersal events out of East Africa into Eurasia. During this period, ephemeral deep-freshwater lakes appeared along the whole length of the EARS, fundamentally changing the local environment. The relationship between the local environment and hominin brain expansion is less clear. The major step-wise expansion in brain size around 1.9 Ma when Homo appeared was coeval with the occurrence of ephemeral deep lakes. Subsequent incremental increases in brain size are associated with dry periods with few if any lakes. Plio-Pleistocene East African climate pulses as evinced by the paleo-lake records seem, therefore, fundamental to hominin speciation, encephalisation and migration.     

New evidence for hominin carcass processing strategies at 1.5 Ma, Koobi Fora, Kenya

Reconstruction of early Pleistocene hominin carcass acquisition and processing behaviors are necessarily based at least in part on butchered fossil bones. This paper provides zooarchaeological and taphonomic analyses and behavioral interpretations of three approximately 1.5 million-year-old archaeofaunas from areas 1A and 103 in the Okote Member of the Koobi Fora Formation, northern Kenya: FwJj14A, FwJj14B, and GaJi14. These sites are all located in similar paleoenvironmental contexts, near shallow water with swampy, seasonally flooded areas, and some evidence for more wooded or gallery forest settings. Both individual specimen--and assemblage-level analyses of butchery-marked bones indicate that the hominins appear to have practiced similar butchery strategies at all of these sites, with butchery (defleshing, disarticulation, and marrow extraction) of both high- and low-ranked skeletal elements with no apparent preference for prey size, skeletal region, limb class, or limb portion. Only four tooth-marked specimens, including one likely crocodile-tooth-marked bone, are preserved in all three archaeofaunas. A paucity of limb epiphyses suggests that bone-crunching hyenids may have deleted these portions subsequent to hominin butchery. Strangely, there are no stone tools preserved with the 292 cut-marked and 27 percussion-marked faunal specimens (out of a total of 6,039 specimens), suggesting that raw material availability may have conditioned hominin lithic discard patterns at these locales. These assemblages increase our knowledge of the dietary behavior and ecology of Homo erectus, and provide support for variability in early Pleistocene hominin carcass foraging patterns.     

Phylogeny and spatio‐temporal diversification of Prunus subgenus Laurocerasus section Mesopygeum (Rosaceae) in the Malesian region

The goals of this study were to reconstruct the phylogeny of Prunus subgenus Laurocerasus section Mesopygeum and to provide a preliminary assessment of its spatio‐temporal diversification in the Malesian region. We inferred the phylogeny using nuclear ITS and ETS and plastid psbA‐trnH, rps16, rpl16, and trnC‐petN sequences. Our analyses support the monophyly of sect. Mesopygeum. Within sect. Mesopygeum, we identified four main subclades: (i) Prunus lancilimba from continental Asia; (ii) Prunus ruthii from Malay Peninsula; (iii) a subclade comprising species from areas centered on the Sunda shelf and also a few species from continental Asia and Wallacea; and (iv) a subclade composed of species from areas of the Sahul shelf, with a small number of taxa also from areas of the Sunda shelf, continental Asia, and the Philippines. We estimated that sect. Mesopygeum originated in continental Asia at c. 44.71 Mya (95% HPD: 31.66–46.90). Nine dispersals between major geographic areas were inferred. From continental Asia, three and two dispersals were inferred to the Sunda shelf and the Sahul shelf in the mid‐Oligocene, respectively. Two dispersals were inferred from the Sahul shelf region to the Sunda shelf in late Oligecene and early Miocene, respectively. There were also two dispersals inferred from the Sunda shelf region, one to the Philippines and one to Wallacea, in the middle and late Miocene, respectively. The diversification in sect. Mesopygeum was likely driven by active geologic events and orogenies in the Neogene in the Malesian region.     

The oldest human fossil in Europe,from Orce (Spain)

The Orce region has one of the best late Pliocene and early Pleistocene continental paleobiological records of Europe. It is situated in the northeastern sector of the intramontane Guadix-Baza Basin (Granada, Andalusia, southern Spain). Here we describe a new fossil hominin tooth from the site of Barranco León, dated between 1.02 and 1.73 Ma (millions of years ago) by Electron Spin Resonance (ESR), which, in combination with paleomagnetic and biochronologic data, is estimated to be close to 1.4 Ma. While the range of dates obtained from these various methods overlaps with those published for the Sima del Elefante hominin locality (1.2 Ma), the overwhelming majority of evidence points to an older age. Thus, at the moment, the Barranco León hominin is the oldest from Western Europe.     

Paleogeographic variations of pedogenic carbonate delta13C values from Koobi Fora, Kenya: implications for floral compositions of Plio-Pleistocene hominin environments

Plio-Pleistocene East African grassland expansion and faunal macroevolution, including that of our own lineage, are attributed to global climate change. To further understand environmental factors of early hominin evolution, we reconstruct the paleogeographic distribution of vegetation (C(3)-C(4) pathways) by stable carbon isotope (delta(13)C) analysis of pedogenic carbonates from the Plio-Pleistocene Koobi Fora region, northeast Lake Turkana Basin, Kenya. We analyzed 202 nodules (530 measurements) from ten paleontological/archaeological collecting areas spanning environments over a 50-km(2) area. We compared results across subregions in evolving fluviolacustrine depositional environments in the Koobi Fora Formation from 2.0-1.5 Ma, a stratigraphic interval that temporally brackets grassland ascendancy in East Africa. Significant differences in delta(13)C values between subregions are explained by paleogeographic controls on floral composition and distribution. Our results indicate grassland expansion between 2.0 and 1.75 Ma, coincident with major shifts in basin-wide sedimentation and hydrology. Hypotheses may be correct in linking Plio-Pleistocene hominin evolution to environmental changes from global climate; however, based on our results, we interpret complexity from proximate forces that mitigated basin evolution. An approximately 2.5 Ma tectonic event in southern Ethiopia and northern Kenya exerted strong effects on paleography in the Turkana Basin from 2.0-1.5 Ma, contributing to the shift from a closed, lacustrine basin to one dominated by open, fluvial conditions. We propose basin transformation decreased residence time for Omo River water and expanded subaerial floodplain landscapes, ultimately leading to reduced proportions of wooded floras and the establishment of habitats suitable for grassland communities.