Evolution of grassland ecosystems during the Late Miocene in the Eastern Mediterranean
Final Report Abstract
This project has investigated the evolution of Late Miocene grassland ecosystems and its importance for mammal evolution and hominid diet in the Eastern Mediterranean (Balkans, Mesopotamia), using palaeobotanical (phytoliths, pollen), but also sedimentological constrains. The most important results are: We demonstrate for the first time that C4 grasses were the dominant herbaceous element during the latest Tortonian (supporting hypothesis #1 and #4), especially in the Pikermi Formation, characterized fire-prone woody grasslands and woodlands within a savannah biome for Pikermi and Pyrgos, supporting early environmental conjectures of Gaudry 1862 and the “Savannah Hypothesis” to explain earliest hominin emergence. Thereby we confirmed the applicability of phytolith indices developed for tropical African vegetation (hypothesis #2). At the Tortonian-Messinian transition (~7.4–7.25 Ma) in the Mediterranean C4 grass ecosystems progressively penetrate the Balkan Peninsula and constitute the environment of the mammal fauna of Pikermi, which contradicts earlier assumptions of sclerophyllous woodlands (verifying our hypothesis # 5). Our results reveal formerly unrecognized Mediterranean environmental changes during the Tortonian-Messinian transition, which provide important constraints for the evolution of mammals, especially hominids as Graecopithecus freybergi. At the Tortonian-Messinian boundary (7.25 Ma), water-stress levels increased and wildfire frequency decreased, which can be interpreted as increasing aridification. Hypothesis # 6-8: Humidity during the latest Tortonian was strongly seasonal with summer dryness and semi-arid ustic to xeric soil moisture with 400 and 600 mm rainfall. In the early Messinian sub-humid soil moisture regimes varied between xeric and udic, corresponding to about MAP of 550-850 mm. In combination with published SST we conclude hot and semi-arid subtropical climate during the late Tortonian and warm Mediterranean type climate conditions during the time of Graecopithecus residence in the earliest Messinian. This potentially non-analogous climate is significant warmer (>4°C) and more humid (up to 50%) than today in this region. Based on phytoliths we inferred a Mediterranean vegetation containing, beside others, Cupressus, Platanus, Myrtus, Tamarix, Arbutus, and prominent herbaceous components, interpreted as Mediterranean savannah, based on the dominance of C4 over C3 grasses. The documented flora contains numerous taxa edible for hominids. Based on palatability, caloric value, biomass and temporal availability we regard Typha elephantina, Quercus robur, and Arbutus unedo as most important for Graecopithecus freybergi. During the late Miocene transient periods of hyperaridity have been developed in Mesopotamia at 8.75, 7.78, 7.5 and 6.25 Ma. Commenced by the desiccation of the Mediterranean and a shrinking Caspian Sea, a sustained hyper-arid period in Arabia (Neogene Arabian Desert climaX, NADX) prevailed from 5.6 to 3.3 Ma. These results clearly support our hypothesis #3 about a non-linear trend towards aridization and increased seasonality, culminating in Mesopotamia in the latest Miocene. Vegetation during the NADX interval was from the herbal halophytic desertic type, dominated by Chenopodiaceae. Our results do not support our hypothesis of grassland vegetation in Mesopotamia at the beginning of sustained Arabian desertification. However, the emergence of deserts in Arabia may had a decisive impact on the evolution and migratory movements of mammals including our human ancestors.
Publications
- 2017. Messinian age and savannah environment of the possible hominin Graecopithecus from Europe. PLoS ONE 12(5): e0177347
Böhme M, Spassov N, Ebner M, Geraads D, Hristova L, Kirscher U, Kötter S, Linnemann U, Prieto J, Roussiakis S, Theodorou G, Uhlig G, Winklhofer M
(See online at https://doi.org/10.1371/journal.pone.0177347) - 2018. Pikermian and post–Pikermian vegetation at the Tortonian-Messinian transition in the Eastern Mediterraneaen. Abstract, RCMNS colloquium, University of Athens (12-14 October 2017)
Kötter, S., Ebner, M., Uhl, D., Böhme, M.
- (2018). The diet of Graecopithecus freybergi: phytoliths and dentognathic evidence. Abstract, American Association of Physical Anthropology (AAPA), Austin, Texas; April 11-14, 2018
Böhme, M., Kötter, S., Fuss, J.
- 2018. Late Miocene stratigraphy, palaeoclimate and evolution of the Sandanski Basin (Bulgaria) and the chronology of the Pikermian faunal changes. Global and Planetary Changes 170
Böhme M, Van Baak, Cgc, Prieto J, Winklhofer M, Spassov N
(See online at https://doi.org/10.1016/j.gloplacha.2018.07.019) - 2021. Neogene hyperaridity in Arabia drove the directions of mammalian dispersal between Africa and Eurasia. Nature Communications Earth & Environment
Böhme, M., Spassov, N., Majidifard, M.R., Gärtner, A., Kirscher, U., Marks, M., Dietzel, C., Uhlig, G., El Atfy, H., Begun, D.R., Winklhofer, M.
(See online at https://doi.org/10.1038/s43247-021-00158-y)
