New radioisotopic datings of volcanic fossil sites are helping researchers unravel the evolution of mammals. The University of Oulu, Finland, is co-leading research that is expected to shed light on early human evolution.

An international research team co-led by the University of Oulu has successfully dated key fossil sites in Central Anatolia, Türkiye, to between 7 and 10 million years ago using a new Argon-Argon (⁴⁰Ar/³⁹Ar) radioisotopic method. In Cappadocia, located at the intersection of continents in Central Anatolia, layers rich in rare fossils have been preserved, mixed with volcanic ash from explosive eruptions.

"While radioisotopic methods are not new in determining the age of fossils, this represents a significant paradigm shift in dating volcanic sedimentary layers that contain mammal fossils," says Academy Research Fellow Ferhat Kaya from the University of Oulu. Kaya co-leads the project.

Previously, the ages of these fossil faunas were estimated based on geographically distant and poorly constrained faunal assemblages between Europe and Asia. This research strengthens Türkiye´s central role in the study of mammalian evolution and highlights the scientific significance of Central Anatolia’s fossil treasures, offering a unique window into mammalian evolution stretching back as far as 12 million years.

According to Kaya, more precise age determinations of mammalian fossils provide new insights into primate evolution. “The research reinforces our understanding of how ecosystems and species evolved during major environmental changes.”

Dating fossils is often challenging due to the lack of volcanic material suitable for radiometric dating in many sedimentary layers. Central Anatolia, however, lies near volcanic centers and is one of the rare geological regions where volcanic ash has preserved a wealth of fossils.

“We are determining the precise ages of fossil-bearing strata. These volcanic deposits contain glassy volcanic grains, which are particularly well-suited for high-precision radiometric dating,” Kaya explains.

Kaya emphasizes that understanding the evolution of fossil mammals depends on both the accurate geological dating of fossil layers and the precise identification of fossil species. While the use of digital fossil databases and computational meta-analyses has become more common, these large databases and methods often rely on imprecise or inconsistent data.

The results obtained through the Argon-Argon (⁴⁰Ar/³⁹Ar) radioisotopic method offer a more accurate timeline for significant mammal fossils, such as the large Miocene ape of the genus Ouranopithecus, potentially a common ancestor of African apes and early bipeds.

“This new research brings much-needed precision to the study of mammal and primate evolution in a region that connects Africa, Asia, and Europe,” says Ferhat Kaya.

The study, Building better biochronology: New fossils and 40Ar/39Ar radioisotopic dates from Central Anatolia, has been published in the prestigious journal Proceedings of the National Academy of Sciences of the United States of America (PNAS) and is partially funded through the Cappadocia Paleontological Expeditions project. https://doi.org/10.1073/pnas.2424428122