Amphibian and reptile fossils to study climate changes

Cristina G. Pedraz/DICYT Knowing climate’s history on Earth is paleoclimatologists’ major objective. These scientists use different techniques to calculate their estimates, as in the case of the analysis of polar ice sheets, tree rings and sediments. Members of the Equipo de Investigación de Atapuerca (EIA) – Atapuerca Research Team- are working on this area: they have studied for years climate evolution from microfauna remains found in paleontological sites at the Atapuerca Mountains, Spain.

This is a new approach to tackle the issue based on changes recorded in microfauna’s composition at the mountain. The team, led by Gloria Cuenca-Bescós, professor at the Universidad de Zaragoza, found at the Gran Dolina site a great source of information because it has an extensive paleontological record allowing to research on the climate of the last million years. As DiCYT was told by Hugues-Alexandre Blain, a researcher at the Institut Català de Paleoecologia Humana i Evolució Social (IPHES) -an institute of human palaeoecology and social evolution in Catalonia, Spain-, a member of this research team also set up by scientists from the Universitat Rovira I Virgili (Tarragona, Spain), the Universidad de Zaragoza and the Centro Nacional de Investigación sobre la Evolución Humana (CENIEH) –a research center on human evolution in Burgos, Spain.

Specifically, Blain has gone in depth into the study of amphibian and reptile communities found at different levels in the Gran Dolina site. Salamanders, frogs, toads, lizards and snakes are being analyzed; their importance lies in two aspects. On one hand, they are animals that remain alive in the Iberian Peninsula while all mammals found "are extinct species". Therefore, by analyzing variations of current amphibians and reptiles and their fossils, "climatic parameters can be calculated".

On the other hand, although it is popularly considered amphibians and reptiles are cold-blooded animals, they regulate their body temperature depending on ambient temperature (unlike mammals that always maintain the same temperature), that is the reason why "they depend so much on water and temperature", and hence, on climate changes.

Recent Studies

Recent studies by this team round off climate data provided by South Pole ice analysis and marine explorations in the Pacific Ocean, where it was found that 450,000 years ago, interglacial or warm periods began to be warmer to date. About two years ago, other scientists analyzed England’s case and found there were not heat peaks after these 450,000 years.

The team in charge of microfauna at the EIA has studied the Mediterranean case and has come to the conclusion that there was a significant change in temperature and rainfall conditions about 450,000 years ago. The amphibian and reptile fossils prior to that date are evidence of the existence on a relatively cold and wet weather, while records after these 450,000 years proved a significant change in weather: higher temperatures and slender rainfall.

The importance of these studies lies on the fact that knowing past climate variations and features is essential to understand human evolution in Europe.

The study of amphibians and reptiles captured a great part of the doctoral thesis by the IPHES researcher, carried out in France between 2001 and 2005. Going forward, he aims to go into two areas: human paleoecology (the study of fossils to reconstruct past environments and ecosystems) and paleoclimatology. "I would like to do research into water, because temperature has caught everybody’s attention, but I believe hominids and fauna have been more related to water than to temperature, especially in the Mediterranean region where droughts can lead to serious consequences," he states.