An investigation carried out by an international team in which the University of Granada (UGR) has participated has studied the evolution of the climate during the Middle Pleistocene in the Iberian Peninsula from the analysis of the fossil amphibians and reptiles that have been recovered in the main deposits with human presence. On the one hand, experts have seen that those amphibians and reptiles of the Middle Pleistocene were practically the same as those that live today, although their distribution has varied .
The UGR prehistorian Juan Manuel Jiménez Arenas is one of the researchers who has carried out the climate study during the Middle Pleistocene (780,000-120,000 years ago) in the Iberian Peninsula. The analyzed fossils cover a time interval that goes from 850,000 years ago to 150,000 years ago .
One of the main conclusions of the research is that in that prehistoric period it rained more than at present, regardless of whether the temperature was higher or lower than the current one in different places. In some cases, such as those of the studied deposits of Cúllar-Baza 1 (Cúllar, Granada) and Cueva Victoria (Cartagena, Murcia), the rainfall was more or less double that of what is currently falling . In the research, which has been led by the paleontologist Hugues-Alexandre Blain, from the Catalan Institute of Human Paleoecology and Social Evolution (IPHES) in Tarragona, José Alberto Cruz Silva, from the Benemérita Universidad Autónoma de Puebla (Mexico), also participated. Vasiliki Margari, from University College London (UK), and Katherine Roucoux, from the University of Saint Andrews (UK).
According to Jiménez Arenas “it is well known that climate changes have been a constant throughout the history of the Earth . Specifically, the period that we are studying presents an important novelty: a global cooling that alternates with warmer periods. These circumstances will significantly condition, sometimes very drastically, the future of living beings. And of all the vertebrate species, the small ones, and especially the cold-blooded ones, such as amphibians and reptiles, are the most sensitive to fluctuations in temperature and rainfall ”.
How can the palaeoenvironment be reconstructed from fossils of frogs, lizards, snakes, and other animals? The amphibians and reptiles of the Middle Pleistocene are practically the same as the current ones , but their distribution has changed. That is why it is important to know where these species live today and under what climatic conditions. From here, scientists establish a range of temperatures and rainfall that is carried over to the past. The authors of the work have also analyzed the difference in temperature between the Pleistocene and current times. 700,000 years ago, in the Granada site of Cúllar, located in the Guadix-Baza basin, the average annual temperature was 4 ºC higher than it is now . On the other hand, in Cal Guardiola (Terrassa, Barcelona), 150,000 years ago it was almost 4 ºC lower. These fluctuations have to do with the climatic alternations that characterize this time period.
The extent of the forests is related to both rainfall and temperatures in the warm months (the more rain and coolness during the summer, the more tree cover). “This fact shows that a characteristic of Mediterranean climates, the summer aridity as a condition for the withdrawal of forest areas, has been accompanying us at least since the Middle Pleistocene,” says Jiménez Arenas. In any case, “ our ancestors could and knew how to adapt to a tremendously changing environment, occupying certainly hostile regions . And this was thanks to an increasingly complex culture, where tools became more specialized and efficient and the use and control of fire more widespread, and a sociability inherited from our ancestors and that can be traced in the Dmanisi site ( Georgia) where the first population that left Africa is registered almost two million years ago ”, concludes the UGR researcher.
Photo caption: material from sediment washing from the Barranco León deposit (Orce, Granada).
