According to previous linguistic work, the Daur language was categorized as a separate language or cluster in nearly all classifications of the larger Mongolic language group. Previous studies showed that many elements of the ancient Mongolic language in the 13^th century are found in the modern Daur language. Here, based on evidence from genetics, history, ethnology, and linguistics, we explored the evolutionary history of the ancestral group of Mongol-speaking populations and provided an accurate timeframe for the early differentiation of Mongolic languages and the emergence of the Daur language as a separate branch. Y-chromosome lineage M401 is one of the paternal founding lineages of all Mongolic-speaking populations. The dominant paternal lineage of Daur, F5483, was one of the oldest sub-branches of M401, while most of the M401 individuals from other Mongolic-speaking populations belong to another lineage, the F3796 or other major sub-branch of M401. These two sub-branches differentiated at about 2,900 years ago. Studies of history, ethnology, and linguistics also revealed a permanent separation between Mongolic tribes who dispersed across the eastern Eurasian steppe and their relatives who remained as hunter-gatherers in the forest since the 9th century. In terms of demographic history, Daur is indeed the oldest branch of all Mongolic-speaking populations. We suggested that the multidisciplinary evidence, especially that of biological anthropology, supports the early branching of the Daur language from the Mongolic language group.