No one really knows for sure. The breed is so ancient, and Tibet has always been so isolated, that it’s impossible to say how or when TMs came to be. We know that for millennia they were the mighty guardians of the Himalayas, and it’s thought that they’re the progenitor of all modern mastiffs. Evidence suggests that early travelers to Tibet were sometimes given these giants as gifts, which were used to create the mastiff breeds of the Middle East and Europe.