Cemetery sites assigned to the Ertebølle culture near such communities as Skateholm and Vedbaek are considered to have the earliest evidence of social ranking in Europe. Several of the Ertebolle sites also have early evidence of dog domestication, among the earliest in Europe.
Many of the Ertebølle sites (such as the type site Ertebølle in Sweden, ca 5800-5100 BP) were built on enormous middens of oyster shell, indicating shellfish were at least a quite substantial part of the Ertebølle diet. Peter Rowley-Conwy has argued that it was the decline in shellfish that convinced the Ertebølle to finally adopt agriculture.
Sources
Mithen, Steven J. 1994. The Mesolithic Age. pp. 79-135 in Prehistoric Europe: An Illustrated History, edited by Barry Cunliffe. Oxford University Press, Oxford.
Rowley-Conwy, Peter. 1984. The Laziness of the Short-Distance Hunter: The Origins of Agriculture in Western Denmark. Journal of Anthropological Archaeology 3:300-324.
This glossary entry is part of the Dictionary of Archaeology. Any mistakes are the responsibility of Kris Hirst.

