Le site Paléolithique supérieur de Yudinovo : résultats des recherches archéologiques des années 2004–2016

The Upper Palaeolithic site of Yudinovo is one of the reference sites, located in the Desna River Basin. Multidisciplinary field studies, organized by the Desna mission (MAE RAS) and conducted between 2004 and 2016, have changed the vision existed so far on the structure and character of the Yudinovo site as well as on the duration of its occupations. The researchers found an ancient ford used by mammoths and other big mammals to cross the river, and a water source was one of the main factors in explaining the location of the Yudinovo site. The site has been occupied in a cyclical way for stays of varied duration. It was frequented by Prehistoric Men during the different seasons, and periods of occupation were apparently of different duration. The stratigraphy of the Yudinovo site reveals two major episodes in the evolution of the site. The dating of the lower archaeological layer dates back to 15,000–13,500 BC. J.C., while the upper layer is attributed to the period of 12,500–12,000 BC. The lower layer, which was formed during the major episode of occupation of the site, is rather thin and shows the complex stratigraphic structure. Various areas of activities, evacuation structures, storage areas with mammoth bones are discovered. Some elements of the lower archaeological layer are perfectly correlated with different episodes of sporadic occupation.     

The Maryland mammoth allele reduces floral stimulus activity in stem piece explants of Nicotiana tabacum (Solanaceae)

The response of axillary buds to floral stimulus activity in stem pieces was examined in two near-isogenic cultivars of tobacco that differ in the recessive maryland mammoth (mm) allele, which confers short-day behavior. All axillary buds from day-neutral plants assayed on six-internode stem pieces made few nodes (less than 20) before flowering, while axillary buds from plants homozygous for mm assayed on six-internode stem pieces either did not flower in noninductive conditions or made many nodes before flowering in inductive conditions. About 80% of day-neutral axillary buds grafted onto day-neutral stem pieces did not respond to floral stimulus in stem pieces, indicating that the floral stimulus in stem pieces is ephemeral. In other graft combinations, the proportion of axillary buds that did respond to floral stimulus in stem pieces was substantially reduced from the 20% of day-neutral buds on day-neutral stem pieces that responded. These results indicate that the mm allele probably reduces both the amount of floral stimulus activity in stem pieces and the competence of axillary buds to respond.     

Forest elephant mitochondrial genomes reveal that elephantid diversification in Africa tracked climate transitions

Among elephants, the phylogeographic patterns of mitochondrial (mt) and nuclear markers are often incongruent. One hypothesis attributes this to sex differences in dispersal and in the variance of reproductive success. We tested this hypothesis by examining the coalescent dates of genetic markers within elephantid lineages, predicting that lower dispersal and lower variance in reproductive success among females would have increased mtDNA relative to nuclear coalescent dates. We sequenced the mitochondrial genomes of two forest elephants, aligning them to mitogenomes of African savanna and Asian elephants, and of woolly mammoths, including the most divergent mitogenomes within each lineage. Using fossil calibrations, the divergence between African elephant F and S clade mitochondrial genomes (originating in forest and savanna elephant lineages, respectively) was estimated as 5.5 Ma. We estimated that the (African) ancestor of the mammoth and Asian elephant lineages diverged 6.0 Ma, indicating that four elephantid lineages had differentiated in Africa by the Miocene–Pliocene transition, concurrent with drier climates. The coalescent date for forest elephant mtDNAs was c. 2.4 Ma, suggesting that the decrease in tropical forest cover during the Pleistocene isolated distinct African forest elephant lineages. For all elephantid lineages, the ratio of mtDNA to nuclear coalescent dates was much greater than 0.25. This is consistent with the expectation that sex differences in dispersal and in variance of reproductive success would have increased the effective population size of mtDNA relative to nuclear markers in elephantids, contributing to the persistence of incongruent mtDNA phylogeographic patterns.     

The flickering genes of the last mammoths

Woolly mammoths, Mammuthus primigenius, are arguably the most iconic of the extinct Pleistocene megafauna, and an abundance of large permafrost‐embedded bone and ivory material ( Fig. 1 ) means they were also among the first to yield credible DNA sequences ( Hagelberg et al. 1994 ; Hoss et al. 1994 ). Despite mammoth remains being numerous throughout northern Eurasia and North America, both the earliest and most recent fossils are found in northeast Siberia, with the last known population being confined to Wrangel Island in the Arctic Ocean from around 10,000 years ago until their extinction around 4,000 years ago. The extent to which these Holocene mammoths were descended from the Pleistocene populations of Wrangel Island and the demographic nature of their terminal decline have, until now, remained something of a mystery. In this issue of Molecular Ecology, Nyström et al. (2012) report the first use of autosomal variation to track the decline of the last mammoths and, in doing so, take a significant step towards resolving these questions. The authors genotyped four microsatellite loci in 59 Pleistocene and Holocene mammoths from Wrangel Island and Chukotka in mainland northeastern Siberia and showed that while the Pleistocene‐to‐Holocene transition is associated with a significant reduction in genetic diversity, subsequent levels of variation remain constant until extinction. Such a pattern is somewhat surprising as it indicates that while the last mammoths were confined to only a few Arctic islands, their final extinction on Wrangel Island was not a gradual process resulting from loss of genetic diversity/inbreeding. Instead, it seems they maintained a viable effective population size of around 500 until near their presumably rapid extinction. While the ultimate agent of mammoth extinction remains unknown, the work of Nyström et al. (2012) . suggests that we should be looking for something sudden, like a rapid change in climate/ecology or perhaps the arrival of humans.

Figure 1 Open in figure viewer PowerPoint Sergey Vartanyan during field collection, holding a woolly mammoth tusk found along a river embankment in northeast Siberia (photographer: Diana Solovyeva).     

The impact of climate change on the structure of Pleistocene food webs across the mammoth steppe

Species interactions form food webs, impacting community structure and, potentially, ecological dynamics. It is likely that global climatic perturbations that occur over long periods of time have a significant influence on species interaction patterns. Here, we integrate stable isotope analysis and network theory to reconstruct patterns of trophic interactions for six independent mammalian communities that inhabited mammoth steppe environments spanning western Europe to eastern Alaska (Beringia) during the Late Pleistocene. We use a Bayesian mixing model to quantify the contribution of prey to the diets of local predators, and assess how the structure of trophic interactions changed across space and the Last Glacial Maximum (LGM), a global climatic event that severely impacted mammoth steppe communities. We find that large felids had diets that were more constrained than those of co-occurring predators, and largely influenced by an increase in Rangifer abundance after the LGM. Moreover, the structural organization of Beringian and European communities strongly differed: compared with Europe, species interactions in Beringian communities before—and possibly after—the LGM were highly modular. We suggest that this difference in modularity may have been driven by the geographical insularity of Beringian communities.     

Pleistocene mitogenomes reconstructed from the environmental DNA of permafrost sediments

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Dietary ecology of the scimitar-toothed cat Homotherium serum

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Fractal dimensions characterizing mammal teeth: a case study involving Elephantidae

1. Dental features frequently have provided data for producing and deducing mammal taxonomies and phylogeny, yet quantitative or statistical analyses for describing intricacies that characterize tooth form are wanting. 2. A method for determining fractal dimensions D that characterize enamel ridges constituting occlusal surfaces for teeth in some mammal species is presented; D quantify complexity (i.e. convolution). The method is exemplified with an analysis that was conducted on teeth from the Family Elephantidae.     

Notes on the Unique Ocher Drawing Discovered at the Mezhyrich Paleolithic Site in Ukraine

The updated examination of the symbolic ocher drawing applied on a mammoth's skull which has been discovered at the Mezhyrich Paleolithic site, has led us to suggest its new interpretation – the drawing reflects an utterly stylized reproduction of a mammoth. The style of the drawing (acute angles) as well as the specific Mezhyrich décor (chevrons, rhombus) are probably based on the V-shaped lower jaw of mammoths which might have been associated with the “female's” triangle. The drawing of a mammoth has been implemented in the manner of “flattened untwisted reproduction” of its two profile projections – that is the method to create a 3-D image on a flat surface.     

Habitats of Pleistocene megaherbivores reconstructed from the frozen fauna remains

The Late Pleistocene landscape in northern Eurasia and North America was inhabited by a specific megafaunal complex, which largely disappeared during the Pleistocene/Holocene transition. Vegetation changes are considered as one of the factors responsible for these extinctions, but the structure and composition of the Pleistocene vegetation are still poorly known. Here we complement previous studies by comparing the taxonomic composition of the plant remains found in the gastrointestinal tracts of the frozen carcasses of Pleistocene megaherbivores with the species composition of the current Siberian vegetation. We compiled a dataset of palaeobotanical records from frozen individuals of Pleistocene megaherbivores found in northern Siberia and Beringia and dated to the period from more than 50 kyr BP to 9 kyr BP. We also compiled a dataset of vegetation plots from several regions in Siberia. We analysed the similarity in taxonomic composition of plants between these two datasets using a novel method that accounts for variable taxonomic resolution in palaeobotanical data. For most megaherbivore individuals, plant remains in their gastrointestinal tracts corresponded to tundra, forest and mire vegetation, while they showed low similarity to steppe. This pattern was relatively constant over time, showing no remarkable differences between the Last Glacial Maximum and the periods before and afterwards. This suggests that during the Upper Pleistocene, a mosaic of mesic and wet vegetation types such as tundra with patches of forests and mires was common in northern Siberia and Beringia. In contrast, the steppe was rare to absent in the landscape or underused by the megaherbivores as a pasture since they found enough food in the widespread mesic and wet habitats with more productive vegetation.