The article continues a series of research works on the ethnic composition of the Buryat population using a case study of the Steppe Dumas, national jurisdictions of the Russian Empire. Presents the study results of the ethnic composition and settlement of Buryats in the Upper Lena Steppe Duma and Lena Authority. The settlement territory of the Upper Lena Buryats is an “origin” land of the biggest tribal union of Buryats – Ekhirits. Ekhirit tribal alliance is the key part in the ethnogenesis of Buryats. Ethnic name “Buryat” firstly was assigned for two tribal alliances – Ekhirid and Bulgad, known as Ekhirit and Bulagat. Also Segenut tribe settled among Upper Lena Buryats. The ancestor of this tribe – Ööludei is the older brother of Buriadai, so this is the evidence of early substrate of Oirat-mongols in Baikal region. A detailed study of the Buryat settlement in the 19th century allows reconstructing the settlement boundary of the Buryat tribes, which are actual for early ethnic history of the region. Analysis of ethnic composition allows reconstructing separate stages of the ethnic history on the examples of small tribes that will expand the analytical material for depth consideration of Buryat ethnogenesis and comparison of the ethnic history of the region with archaeological sites. Based on the archival sources, published sources and field research materials there were reconstructed the ethnic composition and settlement areas of the Upper Lena Buryats in the 19^th century. For the first time the author have compiled detailed maps of the Upper Lena Buryats with an indication of administrative borders and settlements.

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