We consider the development problem of notion «Mesolithic» and the formation of the Mesolithic branch in the Russian archaeological research. We have identified the general dynamical transformation in the scientific rationality (evolutionism, neo-evolutionism). Searching of identification essence of the notion «Mesolithic» comes in two seemingly different research approaches that are identified as stadial concept and concrete-historical approach in the Russian historiographical practice, and we have defined it as research traditions. Every tradition of research is associated with specific Mesolithic mythologeme. In evolutionary – stadial concept, Mesolithic is identified with the microlitization as geometric microliths in neo-evolutionism – concrete-historical concept, the main feature is the changing of hunting objects and the emergence of fishing as the adaptation forms to abrupt climate changes at the boundary of the Pleistocene-Holocene. Neo-evolutionary concept recognizes the role of migration factors and the presence of a temporal differentiation in the development of Mesolithic cultures. Comparative analysis showed that the content and features of the Mesolithic in different research traditions are almost identical, and it is only reflected axiological shift of significance of certain signs to identify the nature of the Mesolithic.