Fallow deer are not native to Britain. Their natural range centres on Anatolia and the eastern Mediterranean, and everything further west is the result of people moving them.
Zooarchaeological work combining ancient DNA, radiocarbon dating and isotope analysis of teeth has resolved a long-standing puzzle. Fallow deer reached Roman Britain in the first century and were kept at high-status sites such as Fishbourne, where strontium isotopes in tooth enamel identify both a first-generation import and an animal born locally, evidence of a breeding herd on the ground rather than a stream of arrivals. That population did not outlast Roman administration. A second introduction in the eleventh and twelfth centuries, associated with Norman deer parks, founded the herds that persist.
The episode makes fallow deer an unusually good tracer of human movement, since each translocation leaves a datable genetic and chemical signature. Precisely which eastern Mediterranean source populations supplied each wave, and why the Roman herds failed while the Norman ones held, are still being narrowed down.