PhD Student, Indian Institute of Science Education and Research
August 11, 2020
Role of Late Quaternary climate and vegetation composition in the evolution of prehistoric humans in India
The Quaternary is known as “Age of Humans” because of the presence of abundant fossil record of Homo species in the geological records. The period has witnessed extraordinary changes in global climate, which resulted in the extinction of many mammalian species and must have controlled or contributed to the evolution of Homo species. Although the fossil records of early Homo species are absent from the Indian subcontinent, varieties of stone tools unearthed from sedimentary deposits of the Quaternary age suggest the presence of tool-making prehistoric humans on the landscape. Based on the study of excavated artefacts and their morphology, it has been suggested that the prehistoric humans of the Indian subcontinent were using the Paleolithic to Neolithic tools. The age of the prehistoric phase varies from global to regional scale and remains a matter of inquisitiveness. Therefore, it is required to have complete control over the age of prehistoric phases before understanding the role of climate on the Homo evolution.
In this direction, we selected the fluvial sections of the Belan valley situated in north-central India that preserved the signature of prehistoric human settlement from Paleolithic (~100 ka) to Neolithic (~3 ka) interval. For the first time, we conducted analyses of oxygen and carbon isotopes in soil carbonates (δ18OSC and δ13CSC) and compound-specific hydrogen and carbon isotopes in leaf wax n-alkanes (δDC29 andδ13CC29) of paleosol from six archaeological sites to understand the climate-cultural relationship. The results suggest several phases of intensified monsoonal rainfall punctuated by drier episodes, which also partly controlled the vegetation composition in the last ~100 ka. Our study reveals the role of climate and vegetation in controlling the prehistoric population or local migration during the Middle Paleolithic to Early Neolithic phase.
Postdoc, University of Bristol
August 18, 2020
Extending CO2 estimates in the geologic record using a chlorophyll-based CO2 proxy
As the concentration of atmospheric carbon dioxide (pCO2) continues to rise along with the increasing demands from our growing population, we need to understand the precise relationship between pCO2 and climate (aka climate sensitivity) to brace for the future. Over the past one million years, pCO2 has shown a striking relationship with temperature, as recorded in air bubbles trapped in ice cores. However, beyond the one-million-year ice core record, we must rely on proxies to reconstruct pCO2, i.e. physically preserved material which reflect an environmental parameter. Developing and calibrating proxies remains a challenge, with different proxies suggesting different values throughout time. To provide geologic context for climate sensitivity, we need to better constrain proxy uncertainty.
Here, we apply this proxy over the mid-Miocene Climatic Optimum (16.9 to 14.7 Ma) for several reasons: 1. It may be an analogue for the near future, 2. It seems to behave differently than other climates in time, and 3. It has highly varied pCO2 estimates during this time. We use a refreshed approach to reconstruct pCO2 from the stable carbon isotopic fractionation that occurs during photosynthesis. Possibly providing a more universal pCO2 proxy (both in time and location) in the geologic record, we develop and test the potential of the organic geochemical compounds that are many by most phytoplankton: phytane, a degradation product of the vital pigment chlorophyll that can be found in all photoautotrophs e.g. plants and algae and cholestane, a degradation product of cholesterol found in all (and only) eukaryotes. This refreshed approach, combined with global temperatures, is used to calculate climate sensitivity. We find that this period is not in fact exceptional and its climate sensitivity is firmly within the standard IPCC estimates, thus resolving the enigma of the warm mid-Miocene.
Postdoc, The Open University
August 25, 2020
PhD Student, University of Kansas
September 1, 2020
Emanuela di Martino
Postdoc, University of Oslo
September 7, 2020
Postdoc, Rutgers University
September 15, 2020
Gabi Serrato Marks
September 22, 2020