Rashid al-Din asserts that Temüjin lived to the age of 72, placing his year of birth at 1155. The Yuanshi (元史, History of the Yuan dynasty, not to be confused with the era name of the Han Dynasty), records his year of birth as 1165. According to Ratchnevsky, accepting a birth in 1155 would render Genghis Khan a father only at the age of 30, and would imply that at the ripe age of 72 he personally commanded the expedition against the Tanguts. Also, according to the Altan Tobci, Genghis Khan's sister, Temulin, was nine years younger than he; but the Secret History relates that Temulin was an infant during the attack by the Merkits, during which Genghis Khan would have been 18, had he been born in 1155. Zhao Hong reports in his travelogue that the Mongols he questioned did not and had never k