In Who is my neighbor? Social affinity in a modern world, Boston College professor, James Allan Vela-McConnell explores the emergence of the concept of "social affinity" bridging classical sociology and social psychology, identifying "the notion of social cohesion" based upon the sentiment of moral obligation.[1]
For instance, both mtDNA and Y chromosome polymorphisms shows a noticeable genetic affinity between Swedes and central Europeans, especially Germans. These conclusions are also valid for Norwegians[1]