Amplitudes of orbitally induced climatic cycles and patterns of hominin speciation

Palaeoanthropologists and archaeologists have long invoked climate change to explain aspects of human evolution. Collection of new climatic and environmental data combined with new fossil discoveries and methodological improvements continue to make exploration of this link a vital endeavour in studying human evolution. The current study employs a global climatic dataset and a rigorously compiled catalogue of hominin first and last appearance dates to test the effects of changes in temperature on hominin speciation and extinction. Through the use of wavelet analysis and bandpass filters the eccentricity, obliquity, and precession components of the studied climatic record are extracted and tested independently for associations with patterns of speciation and extinction. Results suggest that all three components may play a role in speciation events, but that only the obliquity cycle shows a statistically significant relationship with extinction events. It is suggested that, whilst climatic factors could contribute to the appearance of new hominin species, subsequent competition between these species may lead to their extinction.     

An 8000-year history of landscape,climate, and copper exploitation in the Middle East: the Wadi Faynan and the Wadi Dana National Reserve in southern Jordan

Investigations of geomorphology, geoarchaeology, pollen, palynofacies, and charcoal indicate the comparative scales and significance of palaeoenvironmental changes throughout the Holocene at the junction between the hyper-arid hot Wadi 'Arabah desert and the front of the Mediterranean-belt Mountains of Edom in southern Jordan through a series of climatic changes and episodes of intense mining and smelting of copper ores. Early Holocene alluviation followed the impact of Neolithic grazers but climate drove fluvial geomorphic change in the Late Holocene, with a major arid episode corresponding chronologically with the ‘Little Ice Age’ causing widespread alluviation. The harvesting of wood for charcoal may have been sufficiently intense and widespread to affect the capacity of intensively harvested tree species to respond to a period of greater precipitation deduced for the Roman–Byzantine period – a property that affects both taphonomic and biogeographical bases for the interpretation of palynological evidence from arid-lands with substantial industrial histories. Studies of palynofacies have provided a record of human and climatic causes of soil erosion, and the changing intensity of the use of fire over time. The patterns of vegetational, climatic change and geomorphic changes are set out for this area for the last 8000 years.     

A case of valgus ankle in an early Pleistocene hominin

Bipedal locomotion is a defining character of the hominin lineage. A skeletal correlate of bipedality is a perpendicularly oriented tibia relative to the plane of the ankle joint, positioning the foot directly under the centre of mass. Non‐human primates, in contrast, possess a tibial shaft that tilts laterally away from the plane of the ankle joint (valgus ankle), which positions the foot in inversion and is adaptive for arboreal climbing. KNM‐ER 2596 is a small distal tibia from 1.9 mya sediments at Koobi Fora, Kenya. Though it possesses some morphologies functionally linked to bipedality, such as an expanded metaphysis, it also possesses a valgus tilt to the ankle. We test the competing hypotheses that the KNM‐ER 2596 tibia is from a cercopithecoid, a non‐human hominoid, or a pathological hominin. A survey of the orthopaedic literature and a comparative study of modern human and non‐human primate tibiae support the hypothesis that KNM‐ER 2596 is from a hominin. In order to investigate the non‐phylogenetic causes of valgus ankle, we examined human skeletal tibiae with valgus tilt secondary to fracture of the distal fibula. Untreated breaks of the lower third portion of the fibula during childhood can result in a valgus tilt to the distal tibia and occasionally other peculiar morphologies found in the KNM‐ER 2596 tibia such as a superoinferiorly atrophied medial malleolus. The morphology of this tibia is incompatible with hypotheses that it is from a cercopithecoid or a hominoid, and instead, we suggest that KNM‐ER 2596 belonged to a hominin that may have suffered a fracture of the lower left fibula as a juvenile. Copyright © 2010 John Wiley & Sons, Ltd.     

Could woodworking have influenced variation in the form of Acheulean handaxes?

The relationship between tool form and function is fundamental to hominin behaviour and evolution. Acheulean handaxes are known for their general consistency across more than a million years and three continents, albeit with some variation in size and shape. However, the influence of this variation on cutting has only rarely been studied, mostly in either butchery or generalized cutting tasks. Yet evidence indicates that handaxes were used for woodworking by at least 1.5 mya. Here, we experimentally tested whether woodworking could have exerted selective pressures on handaxe form. Additionally, these data were compared with a previous experiment that tested flakes during woodworking. For handaxes, no significant relationships were detected in woodworking efficiency. Accordingly, woodworking likely did not exert strong selective pressures on handaxe variability. However, the effectiveness shown by handaxes further demonstrates the functional flexibility of this technology, which is likely a factor contributing to their use over broad temporal, geographical and ecological spans. When comparing handaxes with flakes, only the smallest flakes were found to be significantly less efficient than handaxes. Therefore, the functional demands of woodworking were likely influencing hominin technological decisions about flake morphology, or the selection of flakes for woodworking, more than they were handaxe morphology.     

Bronze Age upland settlement decline in southwest England: testing the climate change hypothesis

The division of land on Dartmoor during the Bronze Age by the construction of moor-wide boundaries known as reaves represents a significant development in agricultural practice and land tenure. Previous research relating to the Dartmoor reaves suggests this way of life may have continued for no longer than 200–400 years. It has been suggested that their abandonment occurred as the result of a deteriorating climate, although there are no published palaeoclimatic reconstructions from the area. We therefore test the hypothesis that on Dartmoor, a marked climatic deterioration occurred in the late Bronze Age that can be linked to the abandonment of the reaves. A palaeoclimatic reconstruction derived from testate amoebae and peat humification analyses is presented from Tor Royal Bog, central Dartmoor, the first such record from southwest England. A major shift to a cooler and/or wetter climate is inferred from ca. 1395 to 1155 cal BC that is coincident with the period hypothesised as encompassing the abandonment. This climatic deterioration is replicated in sites in northern Britain, suggesting it was a widespread event. It is concluded that while the evidence supports a climatically forced retreat, there are a range of other socio-economic factors that must also be taken into consideration.     

Investigating the role of food processing in human evolution: a niche construction approach

While it is generally agreed that food processing has had a role in human evolution, the specific ways that is has affected our evolution are not well understood. Using a Niche Construction Theory (NCT) perspective, coupled with methodologies borrowed from “post-harvest” research in the plant sciences, this paper investigates the means and mechanism by which food processing is of evolutionary consequence. The central tenet of NCT is that organisms have an active role in their own evolution through reciprocal interactions with their environments; niche construction is understood to occur when organisms initiate long-term changes to their environments that modify the selection pressures on themselves and their descendants (and on other organisms in the environment). Humans and our hominin ancestors are considered to be the ultimate niche constructors due to our ability to modify selection pressures through diverse culturally generated and transmitted cultural means, i.e. cultural niche construction. In this paper, post-harvest methods are used to identify how food processing could feasibly have permitted hominins to modify their evolutionary selection pressures. Food processing is shown to facilitate access to increasing amounts of digestible nutrients and energy (kilocalories/kilojoules) as well as promoting increased dietary breadth and making possible the production of safer and more stable foods. It is argued that these advancements catalysed related technological and ecological skills and knowledge, which together with the nutritional benefits, further triggered changes in hominin brain and body and locomotory adaptations and increased longevity, disease prevention and juvenile survival rates.     

A cultural proxy for drought: ritual burning in the Iron age of Southern Africa

In traditional Bantu-speaking societies in southern Africa, drought is caused by breaches in rules of pollution. At times of severe drought (3–5 consecutive seasons), rainmakers ascend special hills to perform special rituals. The archaeological signature of this unique activity forms a cultural proxy for drought. New research shows that burnt daga structures also correlate with high δ¹⁵N values for small stock. Burnt structures thus form a new component to the proxy. According to the ethnography, farmers implicated in the cause burnt their grain bins, and sometimes houses, as a ritual of cleansing. The dating of these structures provides a revised climatic sequence for the plateau portion of the summer rainfall region. Among other new results, there was a drought at the end of the Mapungubwe period (ca. AD 1300). At about AD 1650, droughts associated with the arrival of maize caused people to stop growing it as food for a while.     

Holocene land-use evolution and associated soil erosion in the French Prealps inferred from Lake Paladru sediments and archaeological evidences

A source-to-sink multi-proxy approach has been performed within Lake Paladru (492 m a.s.l., French Prealps) catchment and a 6-m long sediment sequence retrieved from the central lacustrine basin. The combination of minerogenic signal, specific organic markers of autochthonous and allochthonous supply and archaeological data allows the reconstruction of a continuous record of past human disturbances. Over the last 10,000 years, the lacustrine sedimentation was dominated by autochthonous carbonates and the watershed was mostly forest-covered. However, seven phases of higher accumulation rate, soil erosion, algal productivity and landscape disturbances have been identified and dated from 8400 to 7900, 6000 to 4800, 4500 to 3200, 2700 to 2050 cal BP as well as AD 350–850, AD 1250–1850 and after AD 1970. Before 5200 cal BP, soil erosion is interpreted as resulting from climatic deterioration phases towards cooler and wetter conditions. During the Mid-Late Holocene period, erosion fluxes and landscape disturbances are always associated with prehistorical and historical human activities and amplified by climatic oscillations. Such changes in human land-used led to increasing minerogenic supply and nutrients loading that affected lacustrine trophic levels, especially during the last 1600 years. In addition, organic and molecular markers document previously unknown human settlements around Lake Paladru during the Bronze and the Iron Ages.     

A late Holocene pollen record from Lake Almalou in NW Iran: evidence for changing land-use in relation to some historical events during the last 3700 years

A pollen diagram was prepared from Lake Almalou, a volcanic crater wetland located on the eastern flanks of the Sahand Volcanic Complex in NW Iran. The core provides a 3700-year record of human activity and environmental change in an upland region. We attempt to relate vegetation changes to both climatic change and historical events. Variations of anthropogenic pollen indicators suggest several phases of intensified human activities. Two strongly expressed agricultural phases are dated at about 2450–2220 cal BP (Achaemenid Empire) and 230–30 cal BP (collapse of Safavid Dynasty to the modern period). Historical rather than climatic events appear to be the main controlling factors for upland land-use dynamics. Fruticulture has been practiced in the region at least since the Iron Age, reaching its maximum importance 1500–1250 cal BP during the reign of Sassanid Empire; it declined by the time of Islamic conquest of Iran (651 AD). The Little Ice Age is tangibly recorded by higher lake water levels most probably due to both lower summer temperatures and higher annual precipitations. Low values of cereal-type and cultivated tree pollen during this period may indicate a change in the lifestyle from the cultivation of fields and orchards to a more nomadic life dominated by summer pasture. The modern period (1850 AD onwards) is characterized by expansion of agricultural activities to upland areas and intensified pastoralism.     

Climate change and Zhou relocations in early Chinese history

In Chinese history, the development of the Zhou tribes and the dynasties that succeeded them between 3550 and 2200 BP in the middle reaches of the Yellow River is known as the period of ‘Five Relocations’. Most of these relocations appear to have been forced by the pressure of nomadic invasions and occupations from the northern steppe. Historians simply attributed these relocations to political and military causes. However, palaeoclimatic studies show that the Zhou tribes and their successor dynasties developed at the demise of the Holocene Climatic Optimum when regional climate became highly variable and unstable. An integrated analysis of environmental change over the Loess Plateau and the Mongolian steppe facilitates a credible understanding of the linkage between climatic events and these relocations. It indicates that the relocations caused an expansion or contraction of the settled regions over the drought-prone semi-arid lands. During climatic amelioration, dry farming societies pushed upward to the Loess Plateau where increased precipitation and soil moisture allowed cereals to be cultivated. When hit by droughts and the associated disasters, both the dry farming societies and the nomadic tribes had to move southward to find an environment suitable for their food production. Migration and relocation were, therefore, basic strategies to secure the resources necessary to sustain an agricultural economy. The settled frontier was pulled back as dry farming societies from the upland plateau retreated to the lowland riverbanks of the Guanzhong Basin. Even though there were political and military intentions, climatic events played an essential role in the relocations of the Zhou tribes and the successive dynasties.     

Oldowan behavior and raw material transport: perspectives from the Kanjera Formation

The archaeological record of Oldowan hominins represents a diverse behavioral system. It has been suggested that exploitation of lithic resources by Oldowan hominins was simplistic and represented mostly use of local sources of stone. Here we investigate the raw material selection and transport behaviors of Oldowan hominins reflected in the stone artifact assemblages from the Kanjera South Formation, South Rachuonyo District, Kenya. Using geochemical methods (ED-XRF) artifacts are linked to primary and secondary source outcrops throughout southwestern Kenya. These data show that hominins selected raw materials for transport at frequencies that are significantly different from their availability on ancient landscapes. Furthermore, a substantial proportion of the assemblage represents transport over relatively long distances (>10 km). Our study further suggests that in the early stages of stone tool use hominins used a wide variety of raw materials and selected these materials at some distance from their eventual discard locations. Early hominin behavior may have incorporated an understanding of raw material source distributions across a more extensive landscape than has been previously documented. This supports the growing perspective that Oldowan technology represents a more complex behavioral pattern than is usually associated with the beginnings of hominin tool use.     

Buried assumptions: Some problems in the interpretation of the “Younger Fill” raised by recent data from Greece

A distinctive “Younger Fill” has been identified in the Mediterranean and adjacent regions. The dominant explanation for it is that of climatic change, first advanced by Vita-Finzi in 1960. Recent work on Greece by Bintliff appears to support the hypothesis. However, there are weaknesses. The present paper isolates the assumptions upon which the climatic hypothesis rests, particularly the notion of synchroneity and the apparent need for a universal mechanism. It sets out the grounds for scepticism, which include the ambiguity of the data, and attempts to evaluate the recent evidence from Greece. The paper then proceeds to argue that an anthropogenic origin cannot be ruled out and that it merits serious consideration. Criteria are suggested which the reinstated explanation would need to meet.     

The Dendroecological Potential of Eucalyptus Camaldulensis Dehnhardt (River Red Gum) from the Barmah Forest,Victoria, Australia

The study of tree rings has been used for over 100 years to inform climatic and geomorphological reconstructions. In mainland Australia, no tree species are currently recognised as providing reliable sources for such studies over extensive areas. Eucalyptus camaldulensis is a widely growing species with a growth pattern that is closely linked to high levels of available moisture, such as that associated with floods. The species therefore has the potential to provide palaeoclimatic information that may be of use in hydrological and geomorphological studies. This study initially examines the microstructure of samples of E. camaldulensis taken from the Barmah Forest to assess the applicability of the species to dendroecological investigation. It is found that samples of the species exhibit ring‐like structures, although there are areas of the samples that contain zones of growth without clear ring boundaries. The patterns of growth rings and zones are found to be common to many trees at a site, although the level of variability of pattern from tree to tree is high. Options for future development of the approach described here are to combine ring studies with isotopic‐based analysis to provide a combination of tree age and climatic history.     

Mobility patterns and core technologies in the Middle Paleolithic of the Levant

Mobility is thought to be a significant source of Middle Paleolithic archaeological variability in the East Mediterranean Levant. However, models of Levantine Middle Paleolithic land-use have historically been based on rare and taphonomically sensitive evidence from a limited number of sites. Because lithic artifacts are the most ubiquitous archaeological remains available to the prehistorian, relationships between stone tool technology and mobility patterns can improve tests of hypotheses about prehistoric land-use strategies. This paper examines variation in Middle Paleolithic mobility strategies in the Levant from the perspective of core technology. A model linking expedient core reduction techniques and decreased mobility is adapted from one developed for late prehistoric contexts in the New World. Incorporating core data from numerous Levantine Middle Paleolithic assemblages, this study tests hypotheses about diachronic change, synchronic geographic variation, and possible hominin behavioral differences in mobility strategies.     

Climatic Change

The methods of physical climatology are used to explain climatic variations during the contemporary epoch and in the geological past. Contemporary climatic change is found to depend to a considerable extent on variations in atmospheric transparency. These variations, which change the amount of solar radiation reaching the earth's surface, are associated with the changeable level of volcanic activity. Climatic changes in the geological past are also explained in terms of variations in atmospheric transparency and the changing distribution of the earth's land and sea areas, which influenced circulation in the hydrosphere. On the basis of established regularities in past climatic change, the possible future trend of climatic evolution is suggested. Although the current cooling trend could conceivably lead to renewed expansion of glaciation, this is considered highly unlikely in view of the increasing amount of heat generated by man's growing use of energy. The additional heat may be sufficient in the long run to melt the polar ice and introduce a climate into the middle and high latitudes typical of warm interglacial epochs. Actually, even before this, technology may enable man to eliminate the polar ice artificially. The beneficial and harmful effects of such as step are briefly considered.     

Detecting the effects of selection and stochastic forces in archaeological assemblages

Detecting and diagnosing the causes of change through time in archaeological assemblages is a core enterprise of archaeology. Evolutionary approaches to this problem typically cast the causes of culture change as being either stochastic in origin, or arising from selection. Stochastic sources of change include random innovations, copying errors, drift and founder effects among dispersing groups. Selection is driven by differences in payoffs between cultural variants. Most efforts to identify these evolutionary forces in the archaeological record have relied on assessing how well the predictions from a neutral-stochastic model of cultural transmission fit a data set. Selection is inferred when the neutral-stochastic model fits poorly. A problem with this approach is that it does not test directly for the presence selection. Moreover, it does not account for the fact that both neutral-stochastic and selective forces can act at the same time on the same cultural variants. A different approach based on the Price Equation allows for the simultaneous measurement of selective and stochastic forces. This paper extends use of the Price Equation to the analysis of selective and stochastic forces operating on multiple artifact types within an assemblage. Ceramic data presented by Steele et al. (2010, Vol. 37(6): 1348–1358) from the Late Bronze Age Hittite site of Bo?azköy-Hattusa, Turkey, provide an opportunity to evaluate the efficacy of this model. The results suggest that selection is a dominant process driving the frequency evolution of different bowl rim types within the assemblage and that stochastic forces played little or no role. It is also clear, however, that we should be attentive to combinations of direct and indirect selective effects within assemblages consisting of multiple artifact types.     

The Muddle in the Middle Pleistocene: The Lower–Middle Paleolithic Transition from the Levantine Perspective

The terms Lower Palaeolithic and Middle Palaeolithic represent research constructs within which cultural evolution and prehistoric hominin behaviours can be studied, with the transition usually understood as marking a watershed in our evolution: an adaptation with a million-year record of success that gives way to something new. The interpretation of the Lower Palaeolithic Acheulian technocomplex is usually understood as a period of cultural stasis that extends over much of Africa and Eurasia, principally associated with Homo erectus. Those innovations that can be observed occur widely separated from one another in space and time. Yet a closer and more detailed examination of the Middle Pleistocene records from East Africa, southern Africa, Europe and the Levant reveals significant variation in cultural repertoires. A kind of paradox emerges, in which an Old World Lower Palaeolithic, apparently lacking an overall dynamic of distinctive and directed change in terms of cumulative variation over time, nevertheless culminates in a transition which sees the universal appearance of the Middle Palaeolithic. The two main hypotheses that have been advanced to explain the global transition, which happens essentially synchronously, appear mutually exclusive and contradictory. One view is that altered climatic-environmental constraints enabled and encouraged an ‘Out-of-Africa’ dispersal (or dispersals) of a new type of genus Homo. This cultural replacement model has been challenged more recently by the alternative hypothesis of accumulating but unrelated and temporally non-linked regional, and in fact potentially autochthonous, processes. The Levant, by virtue of its position bridging Africa and Eurasia (thus being the region into which any out-of-Africa groups would have had first to disperse into), must be seen as a critical region for assessing the relative merits of these competing hypotheses. This paper deals with the Lower–Middle Paleolithic boundary in the Levant within a long temporal perspective. The Middle Pleistocene record in the Levant enables us to examine the amplitude of variation within each techno-complex, as well as to question whether there are diachronic changes in the amplitude of techno-typological variations as well as changes in the manner by which they appear in the record. The results carry significant implications for understandings of demographic and societal processes during the Lower–Middle Paleolithic transition in the Levant.     

Spatiotemporal dynamics of the Clovis–Folsom transition

Despite the importance of the Clovis–Folsom transition for understanding the history of western North America, its spatiotemporal dynamics remains unclear. Here we report a three-part study in which we investigated the transition using radiocarbon dates from Clovis and Folsom sites. In the first part of the study, we used dates from Folsom site-phases to determine when and where Folsom originated. In the second part of the study, we employed Clovis and Folsom dates in analyses designed to determine whether Folsom spread via demic diffusion or cultural diffusion. In the third part of the study we investigated the velocity of the Clovis–Folsom transition. The analyses suggest that Folsom first appeared around 12,800 calBP in the northern High Plains and spread north and south from there. They also suggest that the spread of Folsom was, at least in part, the result of population expansion. In addition, the analyses indicate that the spread of Folsom was relatively fast for a prehistoric diffusion but well below the maximum velocity that has been estimated for such events. These findings, in turn, have implications for the hypotheses that have been put forward to explain the Clovis–Folsom transition. They refute the idea that the Clovis–Folsom transition resulted from an extraterrestrial impact over northern North America at 12,900 ± 100 calBP but are consistent with the alternative proposal that the transition was a response to climate-driven environmental change.     

Heat treatment in the South African Middle Stone Age: temperature induced transformations of silcrete and their technological implications

It was recently found that silcrete raw material was heat-treated during the South African Middle Stone Age (MSA) for altering its flaking properties. This finding led to hypotheses about the implications for the MSA hunter-gatherers such as the cost of thermal treatment in terms of investment and firewood. To date, these hypotheses lack a solid basis, for data on the thermal transformations of South African silcrete and, hence, the necessary heating procedure and heating environment, is missing. In order to produce such data, we conducted an experimental study within the framework of the Diepkloof project. This work is based on the petrographic, mineralogical and structural analysis of South African silcrete from the West Coast and its thermal transformations. Our results shed light on the nature of these transformations, the ideal heating temperatures and the tolerated heating speed. The processes occurring in silcrete are comparable to flint, i.e. the loss of chemically bound ‘water’ and the formation of new Si–O–Si bonds, but their intensity is less pronounced. Effective heating temperatures are significantly higher than for flint and the heating speed tolerated by South African silcrete is relatively fast. These findings imply that silcrete heat treatment cannot be directly compared with flint heat treatment. Unlike flint, heating silcrete does not require the setup of a dedicated heating environment and may have been performed in the same time as other fire related activities. This would represent only a minor supplementary investment in time and firewood. These results have broad implications for the discussion about technological evolution and the acquisition of specialised knowledge in the MSA.     

Late Devonian gastropods from the Canning Basin,Western Australia

Over 50 identifications of Tertiary pollen are reviewed. The pollen assemblages indicate rain-forest through most of the Tertiary, but the requisites for pollen preservation are biased towards the wetter climates.

The present day geographical affinities of the botanical groups are largely with taxa of the tropical zone and Australia-wide taxa. There is geographic variation in the fossil pollen assemblages when southeastern Australia is compared with Central Australia and Queensland.

The major changes in the fossil floras coincide with climatic change, indicating the influence of climate on the evolution of plant assemblages. The older phytogeographic concepts are inappropriate for the fossil record, especially when considered in conjunction with palaeoclimates and palaeogeography.

It is unfortunate that palynology has given little information of the evolution of floras in drier climatic regimes, or of the evolution of the eucalypts.