In the '60s and '70s my Grandpa kept German Shepherd Dogs. Loved the breed and was an avid collector of historical records, pictures, etc. The GSD, say, of the 1920's was a well-built dog with a straight back and a leg at each corner. Then, for no other reason than aesthetics, it was decided that a more sloping back was desirable. So that's what they bred for. Decades later we ended up with show dogs with this exaggerated posture, weak spines, hip dysplasia and back legs camped out yonder. Still GSDs, no other breed infusion, but skeletally different.
Pugs in 17th century art show a dog longer in both leg and muzzle. They are a very ancient breed. Their genes have been introduced to other breeds, but not vice versa. Then along came the fashion for dogs shorter in both leg and muzzle. They put the most extreme specimens of the breed to eachother and continued on until we get the pug as we recognize it today. Again, no other breed involvement.
I am using dogs as an example because the physical changes are so visual and dramatic. Obviously, changes occur more quickly in a species which can produce more than one offspring per year and which matures early. However, my point remains valid. If physical change can occur within a breed in the space of 200 years, how much could potentially arise in 2,000 years, with or without human intervention. I would not expect an animal of two centuries ago to be an exact carbon copy of what we recognise today. Could be shorter, narrower, longer-legged, who can say?
Anyway, back to business! I recently read an article that might be of interest to you, Eddie. It regarded Phoenician traders and how they may have been responsible for introducing "ponies" to the West Country over 2,000 years BC. I think they used the term "ponies" because of the height of the animals. They traded them for Cornish/Devon metals and these became the animals we know as Exmoor and Dartmoor ponies. Both breeds became isolated and evolved separately to adapt to their different environments. The Phoenicians did not breed the ponies/horses themselves but traded with the Bedouin who, as we know, were master horse breeders.
If that was proven to be the case, perhaps I can take you to task for that dig at Dartmoors. They didn't just pitch up to the mineshaft one Medieval morning looking for work, you know. Logic dictates that there had to have been an evolutionary starting point earlier than that!