Homogeneous life histories of Anchitherium in the face of Miocene climate changes

The fossil record is a critical resource for understanding evolutionary and ecological processes over long periods, including the response of different taxa to environmental variations driven by global changes. During ca. 10 million years, anchitherine horses dwelled in Palaearctic ecosystems, where they faced two different crucial changes in global climate that promoted a shift from warm and tropical to drier, more open and seasonal environments. Based on the modulating effect of the environment on life-history traits, a diversity of life histories among Anchitherium populations would be expected. However, this aspect has never been explored. We analysed the enamel tissue of Anchitherium spp. from several localities throughout the Iberian and Central European Miocene (MN5–MN7/8) to infer their life history. According to the enamel parameters examined, which proved to be very conservative within the genus, the pace of growth is similar and stable across all populations. The stable and homogeneous life history inferred for Anchitherium seems to indicate that the environmental shifts caused by the mid-Miocene climate instability did not lead to significant alterations in the life history strategy exhibited by this genus, which remained rather constant for at least 2 Ma.