[6][7] Even so, archaeogenetics demonstrated that before the Đông Sơn period, the Red River Delta's inhabitants were predominantly Austroasiatic: genetic data from Phùng Nguyên culture's Mán Bạc burial site (dated 1,800 BC) have close proximity to modern Austroasiatic speakers such as the Mlabri and Lua from Thailand, the Nicobarese from India (Nicobar Islands), and the Khmer from Cambodia;[8][9] meanwhile, "mixed genetics" from Đông Sơn culture's Núi Nấp site showed affinity to "Dai from China, Tai-Kadai speakers from Thailand, and Austroasiatic speakers from Vietnam, including the Kinh";[10] therefore, "[t]he likely spread of Vietic was southward from the RRD, not northward.[12] Chamberlain (1998) argues that the Red River Delta region was originally Tai-speaking and became Vietnamese-speaking only between the seventh and ninth centuries AD as a result of emigration from the south, i.e., modern Central Vietnam, where the highly distinctive and conservative North-Central Vietnamese dialects are spoken today.Thus, Ferlus concludes that the Northern Vietic (Viet-Muong) is the direct heir of the Dongsonian, who had resided in the southern part of the Red River Delta and North Central Vietnam from the 1st millennium BC.[4] Furthermore, John Phan (2013, 2016)[14][15] argues that “Annamese Middle Chinese” was spoken in the Red River Valley and was then later absorbed into the coexisting Proto-Viet-Muong, one of whose divergent dialects evolved into the Vietnamese language.The discovery that Vietnamese was a Mon–Khmer language, and that its tones were a regular reflection of non-tonal features in the rest of the family, is considered a milestone in the development of historical linguistics.[23] Sidwell & Alves (2021) propose that the Vietic languages had dispersed from the Red River Delta, based on evidence from loanwords from early Sinitic and extensive Tai-Vietic contact possibly dating back to the Dong Son period.[22] Chamberlain (2018:9)[25] uses the term Kri-Mol to refer to the Vietic languages, and considers there to be two primary splits, namely Mol-Toum and Nrong-Theun.