Interesting. It is not hard to transport fawns for example, so it could well have been done that way and later escapes or releases. Perhaps primitive man semi-tamed red deer. Primitive man must have tried to tame all sorts of species to come up with the successful species ie domesticated over the generations and the less successful species, which were mostly failures. Deer species have been used to tow carts and buggies in more modern times. Primitive man in Northern Scotland only had the choices available from the species resident in those parts.