The response of vegetation on the Andean flank in western Amazonia to Pleistocene climate change

A reconstruction of past environmental change from Ecuador reveals the response of lower montane forest on the Andean flank in western Amazonia to glacial-interglacial global climate change. Radiometric dating of volcanic ash indicates that deposition occurred ~324,000 to 193,000 years ago during parts of Marine Isotope Stages 9, 7, and 6. Fossil pollen and wood preserved within organic sediments suggest that the composition of the forest altered radically in response to glacial-interglacial climate change. The presence of Podocarpus macrofossils ~1000 meters below the lower limit of their modern distribution indicates a relative cooling of at least 5°C during glacials and persistence of wet conditions. Interglacial deposits contain thermophilic palms suggesting warm and wet climates. Hence, global temperature change can radically alter vegetation communities and biodiversity in this region.

The greening of Arabia: multiple opportunities for human occupation of the Arabian peninsula during the Late Pleistocene inferred from an ensemble of climate model simulations

Climate models are potentially useful tools for addressing human dispersals and demographic change. The Arabian Peninsula is becoming increasingly significant in the story of human dispersals out of Africa during the Late Pleistocene. Although characterised largely by arid environments today, emerging climate records indicate that the peninsula was wetter many times in the past, suggesting that the region may have been inhabited considerably more than hitherto thought. Explaining the origins and spatial distribution of increased rainfall is challenging because palaeoenvironmental research in the region is in an early developmental stage. We address environmental oscillations by assembling and analysing an ensemble of five global climate models (CCSM3, COSMOS, HadCM3, KCM, and NorESM). We focus on precipitation, as the variable is key for the development of lakes, rivers and savannas. The climate models generated here were compared with published palaeoenvironmental data such as palaeolakes, speleothems and alluvial fan records as a means of validation. All five models showed, to varying degrees, that the Arabia Peninsula was significantly wetter than today during the Last Interglacial (130 ka and 126/125 ka timeslices), and that the main source of increased rainfall was from the North African summer monsoon rather than the Indian Ocean monsoon or from Mediterranean climate patterns. Where available, 104 ka (MIS 5c), 56 ka (early MIS 3) and 21 ka (LGM) timeslices showed rainfall was present but not as extensive as during the Last Interglacial. The results favour the hypothesis that humans potentially moved out of Africa and into Arabia on multiple occasions during pluvial phases of the Late Pleistocene.

Middle and Late Pleistocene humid periods recorded in palaeolake deposits of the Nafud desert, Saudi Arabia

Present climate in the Nafud desert of northern Saudi Arabia is hyper-arid and moisture brought by north-westerly winds scarcely reaches the region. The existence of abundant palaeolake sediments provides evidence for a considerably wetter climate in the past. However, the existing chronological framework of these deposits is solely based on radiocarbon dating of questionable reliability, due to potential post-depositional contamination with younger 14C. By using luminescence dating, we show that the lake deposits were not formed between 40 and 20 ka as suggested previously, but approximately ca 410 ka, 320 ka, 200 ka, 125 ka, and 100 ka ago. All of these humid phases are in good agreement with those recorded in lake sediments and speleothems from southern Arabia. Surprisingly, no Holocene lake deposits were identified. Geological characteristics of the deposits and diatom analysis suggest that a single, perennial lake covered the entire south-western Nafud ca 320 ka ago. In contrast, lakes of the 200 ka, 125 ka, and 100 ka humid intervals were smaller and restricted to interdune depressions of a pre-existing dune relief. The concurrent occurrence of humid phases in the Nafud, southern Arabia and the eastern Mediterranean suggests that moisture in northern Arabia originated either from the Mediterranean due to more frequent frontal depression systems or from stronger Indian monsoon circulation, respectively. However, based on previously published climate model simulations and palaecolimate evidence from central Arabia and the Negev desert, we argue that humid climate conditions in the Nafud were probably caused by a stronger African monsoon and a distinct change in zonal atmospheric circulation.

Walking in a winter wonderland? Strategies for Early and Middle Pleistocene survival in mid-latitude Europe

Any occupation of northern Europe by Lower Palaeolithic hominins, even those occurring during full interglacials, must have addressed the challenges of marked seasonality and cold winters. These would have included the problems of: wind-chill and frostbite; duration, distribution and depth of snow-cover; reduced daylight hours; and distribution and availability of animal and plant foods. Solutions can essentially be characterised as a ‘stick or twist’ choice: i.e. year-round presence on a local scale vs. extensive annual mobility. However these options, and the ‘interim’ strategies that lie between them, present various problems, including maintaining core body temperature, meeting the energetic demands of mobility, coping with reduced resource availability and increasing patchiness, and meeting nutritional requirements. The feasibility of different winter survival strategies are explored with reference to Lower Palaeolithic palaeoenvironmental reconstructions and on-site behavioural evidence. Emphasis is placed upon possible strategies for (i) avoiding the excessive lean meat protein problem of ‘rabbit starvation’ (e.g. through exploitation of ‘residential’ species with significant winter body fat and/or by targeting specific body parts, following modern ethnographic examples, supplemented by the exploitation of winter plants); and (ii) maintaining body temperatures (e.g. through managed pyrotechnology, and/or other forms of cultural insulation). The paper concludes with a suggested winter strategy.

Genomic evidence for the Pleistocene and recent population history of Native Americans

How and when the Americas were populated remains contentious. Using ancient and modern genome-wide data, we found that the ancestors of all present-day Native Americans, including Athabascans and Amerindians, entered the Americas as a single migration wave from Siberia no earlier than 23 thousand years ago (ka) and after no more than an 8000-year isolation period in Beringia. After their arrival to the Americas, ancestral Native Americans diversified into two basal genetic branches around 13 ka, one that is now dispersed across North and South America and the other restricted to North America. Subsequent gene flow resulted in some Native Americans sharing ancestry with present-day East Asians (including Siberians) and, more distantly, Australo-Melanesians. Putative “Paleoamerican” relict populations, including the historical Mexican Pericúes and South American Fuego-Patagonians, are not directly related to modern Australo-Melanesians as suggested by the Paleoamerican Model.

Paleoamerican Morphology in the Context of European and East Asian Late Pleistocene Variation: Implications for Human Dispersion Into the New World

Early American crania show a different morphological pattern from the one shared by late Native Americans. Although the origin of the diachronic morphological diversity seen on the continents is still debated, the distinct morphology of early Americans is well documented and widely dispersed. This morphology has been described extensively for South America, where larger samples are available. Here we test the hypotheses that the morphology of Early Americans results from retention of the morphological pattern of Late Pleistocene modern humans and that the occupation of the New World precedes the morphological differentiation that gave rise to recent Eurasian and American morphology. We compare Early American samples with European Upper Paleolithic skulls, the East Asian Zhoukoudian Upper Cave specimens and a series of 20 modern human reference crania. Canonical Analysis and Minimum Spanning Tree were used to assess the morphological affinities among the series, while Mantel and Dow-Cheverud tests based on Mahalanobis Squared Distances were used to test different evolutionary scenarios. Our results show strong morphological affinities among the early series irrespective of geographical origin, which together with the matrix analyses results favor the scenario of a late morphological differentiation of modern humans. We conclude that the geographic differentiation of modern human morphology is a late phenomenon that occurred after the initial settlement of the Americas. Am J Phys Anthropol 144:442-453, 2011. (c) 2010 Wiley-Liss, Inc.

Coalescent analysis of mtDNA indicates Pleistocene divergence among three species of howler monkey (Alouatta spp.) and population subdivision within the Atlantic Coastal Forest species, A. guariba

We have used coalescent analysis of mtDNA cytochrome b (cyt b) sequences to estimate times of divergence of three species of Alouatta-A. caraya, A. belzebul, and A. guariba-which are in close geographic proximity. A. caraya is inferred to have diverged from the A. guariba/A. belzebul clade approximately 3.83 million years ago (MYA), with the later pair diverging approximately 1.55 MYA. These dates are much more recent than previous dates based on molecular-clock methods. In addition, analyses of new sequences from the Atlantic Coastal Forest species A. guariba indicate the presence of two distinct haplogroups corresponding to northern and southern populations with both haplogroups occurring in sympatry within Sao Paulo state. The time of divergence of these two haplogroups is estimated to be 1.2 MYA and so follows quite closely after the divergence of A. guariba and A. belzebul. These more recent dates point to the importance of Pleistocene environmental events as important factors in the diversification of A. belzebul and A. guariba. We discuss the diversification of the three Alouatta species in the context of recent models of climatic change and with regard to recent molecular phylogeographic analyses of other animal groups distributed in Brazil.

Pleistovultur nevesi gen. et sp nov (Aves: Vulturidae) and the diversity of condors and vultures in the South American Pleistocene

Pleistovultur nevesi, a new genus and species of a large Vulturidae is described from the Upper Pleistocene or beginning of the Holocene, based on a complete and well preserved right tibiotarsus from the Cuvieri cave deposits, one of the hundreds of caves of the Lagoa Santa region in Minas Gerais state, Brazil. Also described here is a distal half of a left tibiotarsus from Gruta dos Brejoes, a cave in Morro do Chapeu, Bahia state, Brazil, which probably belongs to another not-yet-known genus and species of the Vulturidae. The described material, added to prior literature, is proof of the appreciable diversity of the Vulturidae during the Pleistocene in South America.

ESR dating of pleistocene mammal teeth and its implications for the biostratigraphy and geological evolution of the coastal plain, Rio Grande do Sul, southern Brazil

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Pleistocene mammals from the southern Brazilian continental shelf

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Cryptic lineages and Pleistocene population expansion in a Brazilian Cerrado frog

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Phylogeography and Pleistocene demographic history of the endangered marsh deer (Blastocerus dichotomus) from the Rio de la Plata Basin

The marsh deer is the largest neotropical cervid with morphological and ecological adaptations to wetlands and riparian habitats. Historically, this now endangered species occupied habitats along the major river basins in South America, ranging from southern Amazonia into northern Argentina to the Parana river delta. This particularly close association with wetlands makes marsh deer an excellent species for studying the effects of Pleistocene climatic changes on their demographic and phylogeographic patterns. We examined mitochondrial DNA variation in 127 marsh deer from 4 areas distributed throughout the Rio de]a Plata basin. We found 17 haplotypes in marsh deer from Brazil, Bolivia and Argentina that differed by 1-8 substitutions in a 601 bp fragment of mitochondrial control region sequence, and 486 bp of cytochrome b revealed only 3 variable sites that defined 4 haplotypes. Phylogeny and distribution of control region haplotypes suggest that populations close to the Pantanal area in central Brazil underwent a rapid population expansion and that this occurred approximately 28,000-25,000 years BP. Paleoclimatic data from this period suggests that there was a dramatic increase for precipitation in the medium latitudes in South America and these conditions may have fostered marsh deer's population growth.

Commensal worm traces and possible juvenile thalassinidean burrows associated with Ophiomorpha nodosa, Pleistocene, southern Brazil

The Pleistocene Chui Formation at Osorio (Rio Grande do Sul, Brazil) consists of coastal marine and eolian sands, the former containing abundant and well-preserved Ophiomorpha nodosa burrow systems. Detailed ichnological study has revealed interesting features associated with them. Small-sized Ophiomorpha, here assigned to a new ichnospecies, O. puerilis, are interpreted as possible burrows of juvenile thalassinidean crustaceans probably belonging to the same species as the producers of larger O. nodosa. Additionally, helicoidal burrows with thick, concentrically laminated linings are associated with the walls of O. nodosa. They are assigned to the new ichnospecies Cylindrichnus helix, and they are interpreted as dwellings of commensal annelid worms. The association of these three icbnospecies constitutes a fossil example of the role of thalassinideans as ecosystem engineers able to modify their environment and to create new space and resources usable by other organisms. (c) 2005 Elsevier B.V. All rights reserved.

Fidelity of molluscan assemblages from the touro passo formation (pleistocene-holocene), southern brazil: taphonomy as a tool for discovering natural baselines for freshwater communities

This study is the first assessment of mollusk fossil assemblages relative to the compositional fidelity of modern mollusk living and death assemblages. It also shows that the sedimentary record can provide information on the original, non-human-impacted, freshwater malacofauna biodiversity, based on Late Pleistocene shells. The fossil mollusk assemblage from the Touro Passo Formation (Pleistocene-Holocene) was compared to living and death assemblages of the Touro Passo River, southern Brazil, revealing little resemblance between fossil and live-dead species composition. Although the living and death assemblages agree closely in richness, species composition, and species relative abundances (both proportional and rank), the fossil assemblage differs significantly from both modern assemblages in most of these measures. The fossil assemblage is dominated by the native endemic corbiculid bivalve Cyanocyclas limosa and the gastropod Heleobia aff. bertoniana. These are absent in the living assemblages, and both living and death assemblages are dominated by the alien Asiatic corbiculid C. fluminea, which is absent in the fossil assemblage. The fossil assemblage also contains, overall, a higher proportional abundance of relatively thick-shelled species, suggesting a genuine bias against the thinner- and smaller-shelled species. Our results suggest that contemporary environmental changes, such as the introduction of some alien freshwater mollusk species, together with post-burial taphonomic processes, are the main factors leading to the poor fidelity of the fossil assemblage studied. Hence, the taxonomic composition of the Late Pleistocene mollusks from the Touro Passo Formation probably would show greater similarity to present-day assemblages wherever the mollusk biodiversity is not disturbed by human activities.

Late Pleistocene and Holocene paleoenvironments in ponds and alluvial sediments of Upper Paraná River, Brazil

Freshwater sponge spicules were analyzed as a paleoenvironmental proxy indicator in five cores of ponds and alluvial fan sediments in the Upper Paraná River's left bank, near Querência do Norte town, northwestern of State of Paraná, southern Brazil. Two optically stimulated luminescence (OSL) dates were obtained from sediments of ponds and one radiocarbon (14C) date was obtained from the alluvial fan. Microscopic analysis of spicules preserved in the sediments allowed a determination of freshwater sponge species. The species assemblage provides evidence for dominantly dry conditions in the Upper Paraná River during the Late Pleistocene. A wetter climate phase was recognized at 14C 7,540 yrs BP, with alluvial fan formation commencing at the transition of the dry Pleistocene climate to the Early Holocene wet climate. This wet interval was characterized by a sponge assemblage marked by the presence of the Neotropical families and typically associated with lotic environments. Sponge spicules analysis from pond sediments reject the possibility that lotic environments contributed to pond genesis and evolution. © 2013 by the Sociedade Brasileira de Paleontologia.