I read or heard someplace that if all dog breeds were allowed to breed freely they would all end up looking alike after some years-——similar to Dingoes and Wild Dogs of Africa.
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Probably true for humans to.
If you go to any city in India, you can observe what you said first hand. There will be many packs of dogs running around loose, scavenging for food, and they interbreed freely. Go to any city, and all the dogs look the same, with none of the special features created by selective breeding by humans.