Tibetan dogs, such as the Shih Tzu, very first ancestors are the Gobi Desert Kitchen Midden Dog, dating back to over 10,000 years ago. This dog was quite wild and most were untamed.
Eventually, a new breed evolved from the Gobi Desert Kitchen Midden Dog, which was called the Small Soft-Coated Drop-Eared Hunting Dog.
From the Small Soft-Coated Drop-Eared Hunting Dog then evolved into the Kitchen Midden Dog.
Ultimately the Kitchen Midden Dog, through distinct breeding programs was used to develop the Tibetan Spaniel, the Pekingese, the Japanese Chin, the Papillon, the Pug and the Shih Tzu.
This breed moved from Tibet into China most likely around the time of the Qing Dynasty between 1644 and 1662. the Shih Tzu was referred to as the Lion Dog. The Lion symbol played a large role in Buddhism.
Because the actual lion was not indigenous to China, the Chinese bred their dogs to look as much like a lion as possible.