Teasing apart the joint effect of demography and natural selection in the birth of a contact zone

Vast population movements induced by recurrent climatic cycles have shaped the genetic structure of plant species. This is especially true in Scandinavia that was repeatedly glaciated. During glacial periods trees were confined to refugia, south and east of the ice sheet, from which they recolonized Scandinavia as the ice melted away. This multi-pronged recolonization led to large contact zones in most species. We leverage large genomic data from 5000 trees to reconstruct the demographic history of Norway spruce (Picea abies) and test for the presence of natural selection during the recolonization process and the establishment of the contact zone. Sweden is today made up of two large genetic clusters, a southern one originating from the Baltics and a Northern one originating from Northern Russia. The contact zone delineating these two clusters closely matches the limit between two major climatic regions. This suggests that natural selection contributed to the establishment and the maintenance of the contact zone. To test this hypothesis we first used Approximate Bayesian Computation; an Isolation-with migration model with genomewide linked selection fits the data better than a purely neutral one. Secondly, we identified loci characterized by both extreme allele frequency differences between geographic regions and association to the variables defining the climatic zones. These loci, many of which are related to phenology, form clusters present on all linkage groups. Altogether, the current genetic structure reflects the joint effect of climatic cycles, recolonization and selection on the establishment of strong local adaptation and con-tact zones.

Development of a Novel Multifunctional Cementitious-Based Geocomposite by the Contribution of CNT and GNP

In this study, a self-sensing cementitious stabilized sand (CSS) was developed by the incorporation of hybrid carbon nanotubes (CNTs) and graphene nanoplatelets (GNPs) based on the piezoresistivity principle. For this purpose, different concentrations of CNTs and GNPs (1:1) were dispersed into the CSS, and specimens were fabricated using the standard compaction method with optimum moisture. The mechanical and microstructural, durability, and piezoresistivity performances, of CSS were investigated by various tests after 28 days of hydration. The results showed that the incorporation of 0.1%, 0.17%, and 0.24% CNT/GNP into the stabilized sand with 10% cement caused an increase in UCS of about 65%, 31%, and 14%, respectively, compared to plain CSS. An excessive increase in the CNM concentration beyond 0.24% to 0.34% reduced the UCS by around 13%. The addition of 0.1% CNMs as the optimum concentration increased the maximum dry density of the CSS as well as leading to optimum moisture reduction. Reinforcing CSS with the optimum concentration of CNT/GNP improved the hydration rate and durability of the specimens against severe climatic cycles, including freeze–thaw and wetting–drying. The addition of 0.1%, 0.17%, 0.24%, and 0.34% CNMs into the CSS resulted in gauge factors of about 123, 139, 151, and 173, respectively. However, the Raman and X-ray analysis showed the negative impacts of harsh climatic cycles on the electrical properties of the CNT/GNP and sensitivity of nano intruded CSS.

Super-volcanic eruptions and impacts on hominin evolution

<p>The impact of super volcanic eruptions (Volcanic Explosivity Index 7-8+) on human evolution is a topic that has invited much debate and controversy (Ambrose 1998, Petraglia et al. 2007, 2012; Clarkson et al., 2020), and has typically focused on the impacts on human populations within the last 100-200kya (e.g. Groucutt 2020). What is less well understood is whether there is any clear evidence to show how super-volcanic eruptions, and their subsequent impacts on paleo-environments and climates, may have influenced hominin evolution over the last c. 5mya. Previous studies using first and last hominin appearance dates have suggested that orbitally-induced climatic cycles (eccentricity, obliquity and precession) may play a role in hominin speciation events, but that only obliquity shows any significant relationship with extinction events (Grove 2012a). Firth and Cole (2015) subsequently suggested that selected super-eruptions may have acted as critical enhancers to particular orbital forcing events.</p><p> </p><p>This paper revisits the Firth and Cole (2015) study and presents a comparison of super volcanic eruptions against first and last hominin appearance dates; orbitally induced climatic cycles; global temperature (measured using the LR04 Benthic Stack – Lisiecki and Raymo 2005); and broad technological behavioural changes in order to assess to what extent such eruptions may have impacted, either directly or indirectly, on human evolution at different temporal and geographic scales. Such large eruptive events certainly do seem to disrupt climatic conditions for significant periods of time at a generational level (Harris 2008). Where data is fine grained enough, volcanic activity also seems to impact on human population dispersals, through push and pull factors, and drive changes in the behavioural record (e.g. Groucutt 2020). However, at the broad evolutionary scale, volcanic eruptions do not seem to lead to a significant turnover of hominin species (at least in regard to the resolution of the data currently available). Therefore, we suggest that future work should seek to bring these two perspectives of scale together to better understand super volcanoes in terms of the complex interplay of changing local conditions and their impacts on the broader global picture of human evolution.</p><p> </p><p> </p><p>References:</p><p>Ambrose, S.H., 1998. Late Pleistocene human population bottlenecks, volcanic winter, and differentiation of modern humans. Journal of Human Evolution. 34, 623–651.</p><p>Clarkson, C. et al. 2020. Human occupation of northern India spans the Toba super-eruption ~74,000 years ago. Nature Communications 11: 961.</p><p>Firth C.R. and Cole J. 2015: A review of super-volcano eruptions and their impact on hominin evolution. INQUA XIX Congress: Japan, July.</p><p>Groucutt, H. 2020. Volcanism and human prehistory in Arabia. Journal of Volcanology and Geothermal Research 402: 107003.</p><p>Harris, B. 2008. The potential impact of super-volcanic eruptions on the Earth’s atmosphere. Weather 63 (8): 221 – 225.</p><p>Petraglia, M.D., et al.,  2007. Middle Paleolithic assemblages from the Indian subcontinent before and after the Toba super-eruption. Science 317, 114–116.</p><p>Petraglia, M.D., Korisettar, R., Pal, J.N., 2012. The Toba volcanic super-eruption of 74,000 years ago: climate change, environments, and evolving humans. Quaternary International. 258, 1–4.</p>

The Nesla Gorge and the connection of the Sofia Lake with the Pannonian Basin

The Nesla Gorge is a picturesque flat-bottomed gorge carved by the Gaber River through the limestones of the Slivnitsa Formation west of Nesla village, Dragoman area. Its flattened bottom is evidence for an inter-lake strait between the Gaber Basin and the Nishava-Moravian Basin in Serbia. This is proved by several layers in the Novi Iskar Formation containing mollusks typical of the Pannonian Basin. It is supposed that the main reason is the sea-level fluctuation of the Pannonian Sea due to Milankovitch climatic cycles which caused two-way movement of the water between the two basins through the Nesla Gorge. The geological history of the area, as evidenced by the geomorphological data, shows the important role of the Nesla Gorge for the existence of the Gaber Basin and Sofia Lake during the Pontian and Dacian Ages.

Очерк о климате, болезнях и их влиянии на средневековую демографию

Essay on the impact of climate and diseases on medieval demography The article is devoted to the most important issues of historical and legal medieval studies – the influence of climate and disease on forming the economic and demographic agenda. In particular, the author calls for a more extensive look at the problems of «global warming», given the presence of climatic cycles. Besides, the author emphasizes: political processes and, accordingly, many laws of past years and today are formed under the influence of natural environmental trends. Keywords: Middle Ages, Demography, Global Warming, Influence of Climate, Political Reflections. Очерк о климате, болезнях и их влиянии на средневековую демографию Статья посвящена важнейшим вопросам историко-правовой медиевистики – влиянию климата и болезней на формирование экономико-демографической повестки. В частности, автор призывает смотреть более пространно на проблематику «глобального потепления», учитывая наличие климатических циклов. Кроме того, автор подчеркивает: политические процессы и, соответственно, многие законы прошлых лет и дня сегодняшнего формируются именно под влиянием естественных, энвайронменталистских тенденций.