Solution:
Denmark has played a substantial role in the history of Northern Europe. Through a nationwide scientific outreach initiative, we collected genetic and anthropometrical data from ∼800 high school students and used them to elucidate the genetic makeup of the Danish population, as well as to assess polygenic predictions of phenotypic traits in adolescents. We observed remarkable homogeneity across different geographic regions, although we could still detect weak signals of genetic structure reflecting the history of the country. Denmark presented genomic affinity with primarily neighboring countries with overall resemblance of decreasing weight from Britain, Sweden, Norway, Germany, and France. A Polish admixture signal was detected in Zealand and Funen, and our date estimates coincided with historical evidence of Wend settlements in the south of Denmark. We also observed considerably diverse demographic histories among Scandinavian countries, with Denmark having the smallest current effective population size compared to Norway and Sweden. Finally, we found that polygenic prediction of self-reported adolescent height in the population was remarkably accurate. The high homogeneity of the Danish population could render population structure a lesser concern for the upcoming large-scale gene-mapping studies in the country.
It has played a substantial role in the history of Northern Europe. Like Swedes and Norwegians, Danes are historically linked to the Vikings—the Germanic Norse seafarers whose commercial and military operations marked the Viking Age in European history (793–1066). Through a series of invasions, conquests, and alliances, the Danish Vikings established settlements as far as in Britain, Estonia, the Faroe Islands, Iceland, Greenland, and even Canada. Denmark’s long-lasting historical bond with Sweden and Norway is nicely exemplified in the formation of the Kalmar Union, a state that brought together the three Scandinavian nations from 1397 to 1523 as a response to Germany’s expansionist tendency to the north in Derry 2000.