During the fourth millennium B.C. the northern coast on the Finnish side of the Botnian Bay seems to have experienced major social and economic developments that continued to flourish throughout the third millennium. These are manifested in the form of new asbestostempered wares, an abundance of exotic goods, clusters of semi-subterranean houses in village-like patterns, and the erection of cairns and megastructures. All these features suggest a certain degree of sedentism and social complexity, both probably triggered by a surplus of food and goods provided by especially rich marine resources. After 2000 B.C., however, house clusters disappear, exotic goods become rare, and megastructures cease to be built. Since these cultural phenomena seem to coincide with a period of resource-rich environmental conditions in the region, this paper suggests that the rise and fall of these signs of prosperity or complexity may be related to the availability of maritime resources.