Around the beginning of 4th millennium BC Comb Ceramic culture arrived in Estonia. Until the early 1980s the arrival of Balto-Finnic peoples, the ancestors of the Estonians, Finns, and Livonians, on the shores of the Baltic Sea was associated with the Comb Ceramic Culture. However, such a linking of archaeologically defined cultural entities with linguistic ones cannot be proven, and it has been suggested that the increase of settlement finds in the period is more likely to have been associated with an economic boom related to the warming of climate. Some researchers have even argued that a Uralic form of language may have been spoken in Estonia and Finland since the end of the last glaciation.