The spoken varieties of Chinese are usually considered by native speakers to be variants of a single language. Due to their lack of mutual intelligibility, however, they are classified as separate languages in a family by some linguists, who note that the varieties are as divergent as the Romance languages. Investigation of the historical relationships among the varieties of Chinese is just starting. Currently, most classifications posit 7 to 13 main regional groups based on phonetic developments from Middle Chinese, of which the most spoken by far is Mandarin (with about 800 million speakers, or 66%), followed by Min (75 million, e.g. Southern Min), Wu (74 million, e.g. Shanghainese), and Yue (68 million, e.g. Cantonese). These branches are unintelligible to each other, and many of their subgroups are unintelligible with the other varieties within the same branch (e.g. Southern Min). There are, however, transitional areas where varieties from different branches share enough features for some limited intelligibility, including New Xiang with Southwest Mandarin, Xuanzhou Wu with Lower Yangtze Mandarin, Jin with Central Plains Mandarin and certain divergent dialects of Hakka with Gan (though these are unintelligible with mainstream Hakka). All varieties of Chinese are tonal to at least some degree, and are largely analytic.