The article presents the results of interdisciplinary (archaeological and palaeoecological) studies conducted in 20182021 in the northern part of the Perm Territory at the confluence of the Kosa and Lolog rivers. The main objects of research were the sites of the Mesolithic period and the natural environment of the Late Glacial and Early Holocene. To identify the confinement of archaeological sites to certain landforms within the river valley, the paleochannel method was used. As a result, 2 terraces and a Holocene floodplain were identified. For paleoenvironmental reconstruction palynological and paleocarpological methods were used. The radiocarbon method was used to create a chronological basis for the area of work. The study of the economic activities of Mesolithic groups was based on osteological analysis. In the Late Glacial period the study area was not yet inhabited by ancient people due to unfavorable natural environments. The settlement started only in the second half of the Boreal period of the Holocene, after the formation of the second terrace and the spread of taiga pine and birch forests with the participation of spruce. By this time, the sites of Kosa I and II, located on the banks of the Lolog river were inhabited. The population was mostly engaged in hunting and partly fishing. The natural environments at the beginning of the Atlantic period of the Holocene were still favorable for the existence of human groups here. Formation of the first terrace in the Lolog valley contributed to the colonization of this territory too. The Kosa III site dates back to this time, which population was still mainly engaged in hunting, and probably also fishing. Later, due to the continued lateral migration of the Kosa and Lolog river beds to the east and the emergence of waterlogged floodplains, people left this area and began to inhabit it again only in the Late Holocene.