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Danish, Swedish, German, English, and members of other ethnic groups should sign up with this site to learn how they're related to other families and ethnic groups. Administrators invite people with bonafide Danish ancestry in their Y-DNA and/or mtDNA lineages to participate in the "Denmark DNA Project" as well as the "Danish Demes Regional DNA Project" administered by Diana Matthiesen.
Danish people live in the southern Scandinavian country of Denmark, located to the north of Germany and in the Southern Schleswig region of Germany. Their language is in the North Germanic family and is closely related to Norwegian and Swedish. In the 9th century, Danes were among the fearsome Vikings who travelled by sea to conquer northeastern England and northern France to rule regions that became known as the Danelaw and Normandy respectively.
Especially common Y-DNA (paternal) haplogroups in the "Danish Demes Regional DNA Project" include I1, I1d and I1d1, I2, R1a, and R1b (and subhaplogroups like R1b1a2a1a1a4 which is also known as R-L48), and less common haplogroups include ones within the broad letter groups E, F, G, J, N, Q.
In the "Denmark DNA Project", Y-DNA haplogroups in Denmark-origin lineages include E1b1b1a1b, I2b1, I1, I1d1, J2a4b3, Q1a3, R1a1a, R1b1a2, R1b1a2a1a1, R1b1a2a1a1b4, and certain others.
Y-DNA I1 originated in northern Europe, probably Denmark itself, and is typically found among the Nordic peoples of Scandinavia (Danes, Swedes, Norwegians, Icelanders) and in northern Germany. It is also very common in western Finland.
In the "Danish Demes Regional DNA Project" common mtDNA (maternal) haplogroups are H (including subhaplogroups like H2a2a and H5a1) and U (including the subhaplogroups U5b1 and U5b2), while less common ones include J, K (including subhaplogroups like K1c1b and K1c2), T, and V.
According to The ALlele FREquency Database, 10.8% of the 102 Danish people studied carry at least one T allele in the R151C (rs1805007) gene where TT always causes red hair.
Georgios Athanasiadis, Jade Yu Cheng, B. J. Vilhjálmsson, Frank Grønlund Jørgensen, T. D. Als, S. Le Hellard, T. Espeseth, P. F. Sullivan, C. M. Hultman, Peter C. Kjærgaard, Mikkel Heide Schierup, and Thomas Mailund. "Nationwide Genomic Study in Denmark Reveals Remarkable Population Homogeneity." (EMPAG presentation version, Genetics journal version) A paper presented at the European Society of Human Genetics (ESHG)'s EMPAG 2016 in May 2016. To appear in print in Genetics. First published electronically on August 17, 2016. This autosomal DNA study involves about 800 Danish students (up from the 600 studied in the 2015 paper many of these authors wrote). They confirmed the "remarkable homogeneity of the Danish population" but also found they have some West Slavic ancestry. Excerpts from the Abstract for EMPAG:
"[...] Notwithstanding Denmark’s homogeneity, we observed a clear signal of Polish admixture in the East of the country, coinciding with historical Polish settlements in the region before the Middle Ages. In addition, Denmark has a substantially smaller effective population size compared to Sweden and Norway, possibly reflecting further lack of strong population structure. None of these three Scandinavian countries seems to have suffered a depression due to the Black Death in the Middle Ages. [...]"
Georgios Athanasiadis, Frank Grønlund Jørgensen, Jade Yu Cheng, Peter C. Kjærgaard, Mikkel Heide Schierup, and Thomas Mailund. "Recent genetic history of Denmark." A paper presented at the annual meeting of The American Society of Human Genetics (ASHG) in October 6-10, 2015 in Baltimore, Maryland, U.S.A. The authors used 23andMe and other population distance and admixture tools to study the autosomal DNA of about 600 Danish high school students who documented their ancestry. Identical-by-descent (IBD) analysis was also performed. Excerpts from the Abstract's "Results" section:
"Although Denmark forms a distinguishable cluster from neighboring countries in the PCA plots (compatible with isolation-by-distance), no st[r]ong structure was observed within the country. Similarly, ADMIXTURE revealed high levels of homogeneity in the Danish samples compared to other North European countries. [...] Finally, chromosome painting revealed strong genetic influence from neighboring Nordic (Sweden and Norway) and Germanic (Germany and Holland) countries and negligible influence from Finland, France and Portugal."
Monica Leu, Keith Humphreys, Ida Surakka, Emil Rehnberg, Juha Muilu, Päivi Rosenström, Peter Almgren, Juha Jääskeläinen, Richard P. Lifton, Kirsten Ohm Kyvik, Jaakko Kaprio, Nancy L. Pedersen, Aarno Palotie, Per Hall, Henrik Grönberg, Leif Groop, Leena Peltonen, Juni Palmgren, and Samuli Ripatti. "NordicDB: a Nordic pool and portal for genome-wide control data." European Journal of Human Genetics 18 (2010): pages 1322-1326. Published online on July 28, 2010. Table 1 indicates that the "GenomEUtwin-DK" study contributed 173 samples from "Denmark Females; age range 20-80 years" and a total of 318212 single-nucleotide polymorphism (SNPs). Figure 1a displays genetic variation between the Danish, Swedish, and Finnish populations with 161 Danish samples included there in yellow color. Another version of the same genetic variation map is here. As one would expect, most of the Danish samples cluster close to one another, but some overlap with Swedes too.
Excerpt from the Abstract:
"The current version of NordicDB pools together high-density genome-wide SNP information from ~5000 controls originating from Finnish, Swedish and Danish studies and shows country-specific allele frequencies for SNP markers."
Siiri Rootsi, Natalie M. Myres, Alice A. Lin, Mari Järve, Roy J. King, Ildus A. Kutuev, Vicente M. Cabrera, Elza K. Khusnutdinova, Kärt Varendi, Hovhannes Sahakyan, Doron M. Behar, Rita Khusainova, Oleg Balanovsky, Elena Balanovska, Pavao Rudan, Levon Yepiskoposyan, Ardeshir Bahmanimehr, Shirin Farjadian, Alena Kushniarevich, Rene J. Herrera, Viola Grugni, Vincenza Battaglia, Carmela Nici, Francesca Crobu, Sena Karachanak, Baharak Hooshiar Kashani, Massoud Houshmand, Mohammad H. Sanati, Draga Toncheva, Antonella Lisa, Ornella Semino, Jacques Chiaroni, Julie Di Cristofaro, Richard Villems, Toomas Kivisild, and Peter A. Underhill. "Distinguishing the co-ancestries of haplogroup G Y-chromosomes in the populations of Europe and the Caucasus." European Journal of Human Genetics 20:12 (December 2012): pages 1275-1282. First published online on May 16, 2012. Supplementary Table 1 indicates that 2 of the 110 males from Denmark newly tested in the study, only 1.8%, belonged to the Y-DNA haplogroup G, and both of them had the subclade mutation G-L497 that's also found in nearby Germany (among other places). G originated far to the southeast of Denmark so it's not surprising that it's uncommon among the Danes.
3 Danes participated in the genetic cluster study "Genetic structure in North-Central Europe with the Galore approach (revisited)" (April 1, 2011). The cluster where all 3 Danes belong (called #9 here) was also found among the sole Dutch participant as well as many British and Irish people and some French people. The data was retrieved from the 1000 Genomes Project, the Dodecad Project, the Human Genome Diversity Project (HGDP), and a published paper by Behar et al. (2010).
Medieval Danish DNA was tested in the studies "mtDNA analysis of human remains from an early Danish Christian cemetery." (Kongemarken cemetery) and "Danish Viking DNA Retrieved" (Galdegil burial site).