The European Mesolithic (roughly the period from 8000 B.C to 2700 B.C) testifies to a continuity in human culture from the times of the Ice Age. This continuity, however, was based on continuous adjustment to environmental changes following the end of the last glacial period (about 12,500 years ago). Three broad subdivisions within the northern Mesolithic are known in Scandinavia. The Maglemose Period (7500-5700 B.C.) was a time of seasonal exploitation of rivers and lakes, combined with terrestrial hunting and foraging. The sites from the Kongemose Period (5700-4600 B.C.) are mainly on the Baltic Sea coasts, along bays and near lagoons, where the people exploited both marine and terrestrial resources. Many Kongemose sites are somewhat larger than Maglemose ones. The Ertebolle Period (4600-3200 B.C) was the culmination of Mesolithic culture in southern Scandinavia. By the Ertebolle Period, the Scandinavia were occupying coastal settlements year-round and subsisting off a very wide range of food sources. These included forest game and waterfowl, shellfish, sea mammals, and both shallow-water and deepwater fish. There were smaller, seasonal coastal sites, too, for specific activities such as deepwater fishing, sealing, or hunting of migratory birds. One such site, the Aggersund site in Denmark, was occupied for short periods of time in the autumn, when the inhabitants collected oysters and hunted some game, especially migratory swans. Ertebolle technology was far more elaborate than that of its Mesolithic predecessors, a wide variety of antler, bone, and wood tools for socialized purposes such as fowling and sea-mammal hunting were developed, including dugout canoes up to ten meters long. With sedentary settlement comes evidence of greater social complexity in the use of cemeteries for burials and changes in burial practices. The trend toward more sedentary settlement, the cemeteries, and the occasional social differentiation revealed by elaborate burials are all reflections of an intensified use of resources among these relatively affluent hunter-gatherers of 3000 B.C Mesolithic societies intensified the food quest by exploiting many more species, making productive use of migratory waterfowl and their breeding grounds, and collecting shellfish in enormous numbers. This intensification is also reflected in a much more elaborate and diverse technology, more exchange of goods and materials between neighbors, greater variety in settlement types, and a slowly rising population throughout southern Scandinavia. These phenomena may, in part, be a reflection of rising sea levels throughout the Mesolithic that flooded many cherished territories. There are signs, too, of regional variations in artifact forms and styles, indicative of culture differences between people living in well-delineated territories and competing for resources. Mesolithic cultures are much less well-defined elsewhere in Europe, partly because the climatic changes were less extreme than in southern Scandinavia and because there were fewer opportunities for coastal adaptation. In much of central Europe, settlement was confined to lakeside and riverside locations, widely separated from one another by dense forests. Marry Mesolithic lakeside sites were located in transitional zones between different environments so that the inhabitants could return to a central base location, where for much of the year they lived close to predictable resources such as lake fish. However, they would exploit both forest game and other seasonal resources from satellite camps. For example, the archaeologist Michael Jochim believes that some groups lived during most of the year in camps along the Danube River in central Europe, moving to summer encampments on the shores of neighboring lakes. In areas like Spain, there appears to have been intensified exploitation of marine and forest resources. There was a trend nearly everywhere toward greater variety in the diet, with more attention being paid to less obvious foods and to those that require more complex processing methods than do game and other such resources. Thus, in part of Europe, there was a long-term trend among hunter-gatherer societies toward a more extensive exploitation of food resources, often within the context of a strategy that sought ways to minimize the impact of environmental uncertainty. In more favored southern Scandinavia, such societies achieved a new level of social complexity that was to become commonplace among later farming peoples, and this preadaptation proved an important catalyst for rapid economic and social change when farming did come to Europe.