Liu says his find demonstrates that Zheng He sailed around the world and returned to China by 1418 with precise knowledge not only of continental coastlines, but of interior geographic and cultural features, all of which appear on the map. But these details were well known in China by the time the map was supposedly drawn in the 18th century, argue critics such as Li Xiaocong, a cartography expert at Peking University. "It's simply not logical," says Li, "to use a map drawn in [Emperor] Qianlong's time to prove the existence of a map that might have been drawn during the reign of Yongle"—some three centuries earlier, in the Ming era. Li adds: "We don't even know if that Ming map existed."
Gavin Menzies, the map's most vocal champion, is sure it did. Menzies, a retired British Naval Commander, is the author of 1421: The Year China Discovered America, a book that puts Zheng He's fleet on American shores seven decades ahead of Columbus. Published in 2002, this best seller mixes established fact with Menzies' own much-disputed interpretations of history. It was a Chinese edition of 1421 and subsequent e-mails with Menzies that Liu says convinced him of his map's significance. Menzies, who has helped publicize Liu's find, tells TIME: "There isn't one millionth of a 1% chance the map is a fake."
But a lot about the map, especially its use of language, has led professional historians to view it with suspicion. "If you look at the text, there are really some things that are a bit strange," says Nicolas Standaert, an expert on the Ming era at the Katholieke Universiteit Leuven in Belgium. Standaert points to passages circled in red—which the map's legend says are copied from the 1418 map—that contain words or terms not used at that time. Among them is the map's word for the Christian God and its description of what is now the South China Sea as "the Great Qing Sea," a term not in use until the Qing Dynasty in 1644. "It's always possible that someone will use language differently from his contemporaries," says Standaert, "but I find that there are so many questions from a linguistic point of view that the chances are the map is more recent than it says it is."
Scholars also question the style of the map, a hemispheric projection that the Chinese aren't known to have used until the 16th century. Geoff Wade, a Ming expert at the National University of Singapore, says the map is "clearly a hoax," and was "probably made in the last few years." He observes: "If you've seen any of the maps from Zheng He's voyages, they're in a completely different style."
Liu seems unfazed by such skepticism. Interviewed in his antique-filled Beijing office, he responds with a calm smile. "Just because we don't know what term was used for God, and have no evidence of a word having been used at a certain time, doesn't mean it wasn't used." He says "the Great Qing Sea" was the mapmaker's way of avoiding the taboo of appearing loyal to the previous dynasty. Liu has submitted a sample of the map for carbon dating, but has not yet received the results. Still, even if the bamboo paper's age checks out, it wouldn't rule out a forgery, as old paper can be used to make a new map. Above all, adds Liu, he thinks his treasure is real because "most petty criminals wouldn't have the knowledge to produce this map ... I believe concrete evidence will surface to prove I'm right."
The Chinese media—which, in the past, might have embraced a theory that China beat Europe in exploration—isn't holding its breath. The Shanghai-based Oriental Morning Post opined: "Chinese who are famous for their nationalism did not want to believe their ancestors found America first this time ... This is a perfect example of how China has come to take research more seriously and has grown more realistic and objective." And, it seems, more confident of its place in the world.