A recent study published in iScience reveals that European fallow deer have experienced a significant loss of genetic diversity since the last interglacial period, based on analysis of 120,000-year-old fossils from Neumark-Nord in Saxony-Anhalt, Germany. Researchers from the University of Potsdam, the MONREPOS Research Center, and Leiden University found that modern fallow deer represent only a fraction of the genetic variety present in their Ice Age ancestors. The fossils, preserved in unique lake sediments, allowed for the extraction of ancient DNA from ten specimens, showing that the ancient population had genetic diversity comparable to that of contemporary fallow deer across Eurasia. The study highlights that glacial cooling likely led to the extinction of diverse northern populations, leaving only a single lineage to survive in southern refugia. This lineage has been spread globally by humans throughout history, contributing to the current low genetic variation. The findings suggest that the observed phenotypic variability in ancient fallow deer is due to local adaptation rather than different genetic lineages. Future research may further clarify the species' demographic history.