In the 10th century the Nestorians introduced Christianity into Tartary proper; in 1274 Marco Polo saw two of their churches.
On the other hand they are considerably like the Mongoloid peoples of north and east Asia (less so to the Polynesians); so that the general tendency among anthropologists has been to admit a common origin, however remote, between the tribes of Tartary and of America.
In 1245 the Roman pontiff sent two embassies - one, a party of four Dominicans, sought the commander-in-chief of the Mongol forces in Persia; the second, consisting of Franciscans, made their way into Tartary, and sought to convert the successor of Oktai-Khan.
Both, however, regarded it as a peninsula, and were unaware of the existence of the Strait of Tartary, which was discovered in 1809 by a Japanese, Mamiya Rinzo.
Contemporary observers agree that the disease was introduced from the East; and one eyewitness, Gabriel de Mussis, an Italian lawyer, traced, or indeed accompanied, the march of the plague from the Crimea (whither it was said to have been introduced from Tartary) to Genoa, where with a handful of survivors of a Genoese expedition he landed probably at the end of the year 1347.