Koreans are a people of northeastern Asia. Most Koreans today live on the Korean peninsula: largely in South Korea and, to a considerably lesser extent, North Korea. Evidence sugguests that most of their ancestors once lived in Manchuria and Siberia and were Tungusic and Altaic peoples. The Koguryo people who formed the kingdom of Koguryo spoke an Altaic language; their kingdom included lands in central and northern Korea as well as Manchuria.

Hangeul is the modern Korean alphabet, with 24 letters.

Among Korean males who have been studied, the Y-DNA (paternal DNA) haplogroups O2b* (P49) and O3 (M122) were particularly common. O2b* is found between about 14 and 33 percent of Korean males and may be of Manchurian origin or a nearby region in northeastern Asia. About 7.9 percent of Koreans belong to a branch of O2b known as haplogroup O2b1. O3 is found in about 40 percent of Korean males and may also have connections to Manchuria as well as with rice farmers from southern China. Y-DNA haplogroup C3 may have come to the Koreans from eastern Siberia.

In terms of mtDNA (maternal DNA), the haplogroup D4 is very common among Koreans.

Studies such as "Gene Flow between the Korean Peninsula and Its Neighboring Countries" (2010) were unable to collect DNA samples from North Koreans due to the ongoing political conflict between North and South Korea, but researchers hope to collect North Korean data in the future.

Koreans are racially a purely Mongoloid population. They carry the 1540C allele on their EDAR gene which among other things results in thicker hair than other races. Koreans also have the ABCC11 gene nearly universally so they have dry earwax as opposed to the wet earwax of most people in Europe, the Middle East, and Africa.

Major studies of Koreans

Soon Hee Kim, Myun Soo Han, Wook Kim, and Won Kim. "Y chromosome homogeneity in the Korean population." International Journal of Legal Medicine 124:6 (November 2010): pages 653-657. First electronically published on August 17, 2010. Excerpts from the Abstract:

"The distribution of Y-chromosomal variation from the 12 Y-SNP and 17 Y-STR markers was determined in six major provinces (Seoul-Gyeonggi, Gangwon, Chungcheong, Jeolla, Gyeongsang, and Jeju) to evaluate these populations' possible genetic structure and differentiation in Korea. [...] Based on the result of 12 Y-SNP markers (M9, M45, M89, M119, M122, M174, M175, M214, RPS4Y, P31, SRY465, and 47z), almost 78.9% of tested samples belonged to haplogroup O-M175(including its subhaplogroups O3-M122: 44.3%, O2b*-SRY465: 22.5%, O2b1-47z: 8.7%), and 12.6% of the tested samples belonged to haplogroup C-RPS4Y. A total of 475 haplotypes were identified using 17 Y-STR markers included in the Yfiler kit, among which 452 (95.2%) were individual-specific. The overall haplotype diversity for the 17 Y-STR loci was 0.9997 and the discrimination capacity was 0.9387. Pairwise genetic distances and AMOVA of the studied Korean provinces reflected no patrilineal substructure in Korea, except for Jeju Island. [...]"

Jongsun Jung, Hoyoung Kang, Yoon Shin Cho, Ji Hee Oh, Min Hyung Ryu, Hye Won Chung, Jeong-Sun Seo, Jong-Eun Lee, Bermseok Oh, Jong Bhak, and Hyung-Lae Kim."Gene Flow between the Korean Peninsula and Its Neighboring Countries." PLoS ONE 5(7) (July 29, 2010): e11855. Koreans living in 10 cities in South Korea were included in this study and compared with other Asian populations (Chinese, Japanese, Mongolians, Vietnamese, Cambodians) as well as peoples from Europe, Africa, and the Americas using autosomal DNA. Many Koreans clustered with Japanese people and with Chinese from Beijing and Jilin, but other Koreans (primarily from the Gyeongsang regions) formed a separate cluster that probably represents Siberian admixture. Koreans have a lot more Altaic admixture than Japanese from Japan and Han Chinese from Beijing do. Koreans living on the southwestern tip of Jeju Island have the least amount of Altaic ancestry of all Koreans in South Korea.

Excerpts from the Abstract:

"[...] By extension, the analysis of monomorphic markers implied that nine out of ten historical regions in South Korea, and Tokyo in Japan, showed signs of genetic drift caused by the later settlement of East Asia (South Korea, Japan and China), while Gyeongju in South East Korea showed signs of the earliest settlement in East Asia. In the genome map, the gene flow to the Korean Peninsula from its neighboring countries indicated that some genetic signals from Northern populations such as the Siberians and Mongolians still remain in the South East and West regions, while few signals remain from the early Southern lineages."

Excerpts from the Results section:

"[...] Of the ten historical regions in South Korea, some in SW Korea overlap with those of Japan, while most of the MW Korean regions are located at the center of the genome map. Similarly, in the NJ tree, nodes for SW Korea are close to those in Japan, MW Korea is close to China, and SE Korea is located at the right hand side of the tree. [...] the Middle West area formed a melting pot in the Korean Peninsula because populations moving from South to North, North to South, and from Eastern China, including the SanDung peninsula, to the Middle West in Korea all came together in this region. In the genome map, the signals for MW Korea are also close to those for Peking (CHB) in China. The overall result for the Korea-Japan-China genome map indicates that some signals for Mongolia and Siberia remain in SW Korea and SE Korea, respectively, while MW Korea displays an average signal for South Korea. [...] "

Han-Jun Jin, Chris Tyler-Smith, and Wook Kim. "The Peopling of Korea Revealed by Analyses of Mitochondrial DNA and Y-Chromosomal Markers." PLoS ONE 4(1) (2009): e4210. The mtDNA haplogroup D4 is very common among Korean people. This haplogroup is also prevalent in Siberia. The study found mtDNA haplogroup A in about 10% of the Koreans tested. A is the most frequently encountered mtDNA haplogroup among the Chukchi, Inuit (Eskimo), and Na-Dene peoples as well as many New World Indian (Amerindian) populations from North America and Central America. Meanwhile, the mtDNA haplogroup B is also found in some Koreans and it's also common in China and Japan. Less common Korean mtDNA haplogroups include F, M, R, U, and Z.

An excerpt from the Background section:

"The Koreans are generally considered a northeast Asian group because of their geographical location. However, recent findings from Y chromosome studies showed that the Korean population contains lineages from both southern and northern parts of East Asia."

The "Methodology and Results" section reads:

"We analyzed mitochondrial DNA (mtDNA) sequence variation in the hypervariable segments I and II (HVS-I and HVS-II) and haplogroup-specific mutations in coding regions in 445 individuals from seven east Asian populations (Korean, Korean-Chinese, Mongolian, Manchurian, Han (Beijing), Vietnamese and Thais). In addition, published mtDNA haplogroup data (N = 3307), mtDNA HVS-I sequences (N = 2313), Y chromosome haplogroup data (N = 1697) and Y chromosome STR data (N = 2713) were analyzed to elucidate the genetic structure of East Asian populations. All the mtDNA profiles studied here were classified into subsets of haplogroups common in East Asia, with just two exceptions. In general, the Korean mtDNA profiles revealed similarities to other northeastern Asian populations through analysis of individual haplogroup distributions, genetic distances between populations or an analysis of molecular variance, although a minor southern contribution was also suggested. Reanalysis of Y-chromosomal data confirmed both the overall similarity to other northeastern populations, and also a larger paternal contribution from southeastern populations."

Wook Kim, Tag-Keun Yoo, Dong-Jik Shin, Hyun-Wook Rho, Han-Jun Jin, Eun-Tak Kim, and Yoon-Sun Bae. "Mitochondrial DNA Haplogroup Analysis Reveals no Association between the Common Genetic Lineages and Prostate Cancer in the Korean Population."PLoS ONE 3(5) (May 21, 2008): e2211. Koreans in this study have the following mtDNA haplogroups: D, D4a, D4b, D4, G, M7, M7a, M7b, M8, M8a, M, N, N9, Y, A, B, and F. The D4 haplogroup is their most frequent (13.7% of prostate cancer patients and 13.9% of normal controls). Others found frequently include D4b, D4a, M8a, A, and B.

Wook Kim, Tag-Keun Yoo, Sung-Joo Kim, Dong-Jik Shin, Chris Tyler-Smith, Han-Jun Jin, Kyoung-Don Kwak, Eun-Tak Kim, and Yoon-Sun Bae. "Lack of Association between Y-Chromosomal Haplogroups and Prostate Cancer in the Korean Population." PLoS ONE 2(1) (January 24, 2007): e172. An excerpt from the "Results and Discussion" section:

"The Korean population surveyed here is characterized by a high frequency of [Y-DNA] haplogroup O-M175 (and its sublineages) in both groups of prostate cancer patients (84.0%) and normal controls (76.3%) (Figure 1 and Table 1). This result is consistent with previous reports, showing that most of the east Asian populations share a common genetic feature of high frequencies of haplogroup O-M175-derived chromosomes [20], [24], [25]. The distribution of Y chromosome frequencies studied here was also concordant with previous results from Korean surveys [20], [25]."

H. Y. Lee, J. E. Yoo, M. J. Park, U. Chung, C. Y. Kim, and K. J. Shin. "East Asian mtDNA haplogroup determination in Koreans: haplogroup-level coding region SNP analysis and subhaplogroup-level control region sequence analysis." Electrophoresis 27(22) (November 2006): pages 4408-4418. An excerpt from the Abstract:

"Using two multiplex systems, all 593 Korean mtDNAs were allocated into 15 haplogroups: M, D, D4, D5, G, M7, M8, M9, M10, M11, R, R9, B, A, and N9. As the D4 haplotypes occurred most frequently in Koreans, the third multiplex system was used to further define D4 subhaplogroups: D4a, D4b, D4e, D4g, D4h, and D4j."

Han-Jun Jin, Kyoung-Don Kwak, Michael F. Hammer, Yutaka Nakahori, Toshikatsu Shinka, Ju-Won Lee, Feng Jin, Xuming Jia, Chris Tyler-Smith, and Wook Kim. "Y-chromosomal DNA haplogroups and their implications for the dual origins of the Koreans." Human Genetics 114:1 (December 2003): pages 27-35. First electronically published on September 18, 2003.

Abstract:

"We have analyzed eight Y-chromosomal binary markers (YAP, RPS4Y(711), M9, M175, LINE1, SRY(+465), 47z, and M95) and three Y-STR markers (DYS390, DYS391, and DYS393) in 738 males from 11 ethnic groups in east Asia in order to study the male lineage history of Korea. Haplogroup DE-YAP was found at a high frequency only in Japan but was also present at low frequencies in northeast Asia, including 2.5% in Korea, suggesting a northern origin for these chromosomes. Haplogroup C-RPS4Y(711) was present in Korea and Manchuria at moderate frequencies: higher than in populations from southeast Asia, but lower than those in the northeast, which may imply a northern Asian expansion of these lineages, perhaps from Mongolia or Siberia. The major Y-chromosomal expansions in east Asia were those of haplogroup O-M175 (and its sublineages). This haplogroup is likely to have originated in southern east Asia and subsequently expanded to all of east Asia. The moderate frequency of one sublineage in the Koreans, haplogroup O-LINE1 (12.5%), could be a result of interaction with Chinese populations. The age of another sublineage, haplogroup O-SRY(+465), and Y-STR haplotype diversity provide evidence for relatively recent male migration, originally from China, through Korea into Japan. In conclusion, the distribution pattern of Y-chromosomal haplogroups reveals the complex origin of the Koreans, resulting from genetic contributions involving the northern Asian settlement and range expansions mostly from southern-to-northern China."

Excerpts from the body of the study:

"The haplogroups carrying the M9-G mutation and additional sublineages of M9-G in Korea appear to be at an intermediate frequency (81.9%) between southeast and northeast Asian populations. This result implies that the Korean population may be influenced by both the northeast and southeast Asian populations. Even within haplogroup O, the most frequent Korean STR haplotype (23-10-13 with the markers DYS390-DYS391-DYS393, 19% of haplogroup O; Table 3) is the most frequent in the Philippines (27%), whereas the second most frequent Korean haplotype (24-10-12, 16%) is the most frequent in Manchuria (45%). [...] In this study, the Koreans appear to be most closely related overall to the Manchurians among east Asian ethnic groups (Fig. 2), although a principal components analysis of haplogroup frequencies reveals that they also cluster with populations from Yunnan and Vietnam (Fig. 3). The genetic relationship with Manchuria is consistent with the historical evidence that the Ancient Chosun, the first state-level society, was established in the region of southern Manchuria and later moved into the Pyongyang area of the northwestern Korean Peninsula. Based on archeological and anthropological data, the early Korean population possibly had a common origin in the northern regions of the Altai Mountains and Lake Baikal of southeastern Siberia (Han 1995; Choi and Rhee 2001). Recent studies of mtDNA (Kivisild et al. 2002) and the Y-chromosome (Karafet et al. 2001) have also indicated that Koreans possess lineages from both the southern and the northern haplogroup complex."

Sunghee Hong, Seong-Gene Lee, Yongsook Yoon, and Kyuyoung Song. "Study of Korean Male Origins." Poster presentation #542 in HGM2002 Poster Abstracts: 11. Genome Diversity from HUGO's 7th International Human Genome Meeting, Shanghai, China, April 14-17, 2002. 195 Korean males were tested on their Y-chromosome markers. Excerpts from the summary:

"[...] The Korean males were characterized by a diverse set of 4 haplogroups (Groups IV, V, VII, X) and 14 haplotypes that were also present in Chinese. The most frequent haplogroup in Korean was Group VII (82.6%). It was also the most frequent haplogroup in Chinese (95%) as well as in Japanese (45%). The frequencies of the haplogroups V, IV, and X were 15.4%, 1%, and 1%, respectively. The second most frequent haplogroup V in Korean was not present in Chinese, but its frequency was similar in Japanese."

D. J. Shin, H. J. Jin, K. D. Kwak, J. W. Choi, M. S. Han, P. W. Kang, S. K. Choi, and W. Kim. "Y-Chromosome multiplexes and their potential for the DNA profiling of Koreans."International Journal of Legal Medicine 115:2 (2001): pages 109-117.

N. Saha and J. S. Tay. "Origin of the Koreans: a population genetic study." American Journal of Physical Anthropology 88:1 (May 1992): pages 27-36. This is an old study that didn't use current DNA testing techniques. Excerpts from the Abstract:

"[...] Thirteen polymorphic and 7 monomorphic blood genetic markers (serum proteins and red cell enzymes) were studied in a group of 437 Koreans. Genetic distance analyses by both cluster and principal components models were performed between Koreans and eight other populations (Koreans in China, Japanese, Han Chinese, Mongolians, Zhuangs, Malays, Javanese, and Soviet Asians) on the basis of 47 alleles controlled by 15 polymorphic loci. A more detailed analysis using 65 alleles at 19 polymorphic loci was performed on six populations. Both analyses demonstrated genetic evidence of the origin of Koreans from the central Asian Mongolians. Further, the Koreans are more closely related to the Japanese and quite distant from the Chinese. The above evidence of the origin of Koreans fits well with the ethnohistoric account of the origin of Koreans and the Korean language. The minority Koreans in China also maintained their genetic identity."

The HUGO Pan-Asian SNP Consortium. "Mapping Human Genetic Diversity in Asia."Science 326:5959 (December 11, 2009): pages 1541-1545. Koreans were found to have the least amount of Austronesian DNA compared to other East Asian peoples, even a little less than the Japanese.

Michael F. Hammer, Tatiana M. Karafet, Hwayong Park, Keiichi Omoto, Shinji Harihara, Mark Stoneking, and Satoshi Horai. "Dual origins of the Japanese: common ground for hunter-gatherer and farmer Y chromosomes." Journal of Human Genetics 51(1) (2006): pages 47-58. First published online on November 18, 2005. Japanese males were genetically compared to many peoples, including Koreans. Excerpts:

"All southeastern Asian populations cluster together on the left side of the plot; with only northern Han Chinese, Korean, and Manchu populations showing closer affinities with southeastern groups than with their geographic neighbors. All other northeast Asians, as well as central Asians, south Asians, and Oceanic populations, are on the right side of the plot. [...] The very low incidence of [Y-DNA] D chromosomes in Korea and in Micronesia is likely explained by recent admixture. This is not surprising given that Korea was ruled by Japan from 1910 to 1945 and Micronesia was under Japanese control for more than three decades since 1914 until the end of World War II. The same may be true for the very few O-47z chromosomes found in Korea and Southeast Asia. [...] Haplogroup M12 is the mitochondrial counterpart of Y chromosome D lineage. This rare haplogroup was detected only in mainland Japanese, Koreans, and Tibetans, with the highest frequency and diversity in Tibet (Tanaka et al. 2004). Haplogroup O-SRY465 fits basic criteria (Karafet et al. 1999) for a Yayoi founding lineage [in Japan] because it is widespread in (and almost entirely restricted to) both Japan and Korea. Its higher Y-STR diversity in Korea [...] is consistent with the hypothesis that O-SRY465 tracks male lineages that migrated to Japan from Korea. [...] Y chromosomes that originated in Southeast Asia expanded to Korea and Japan with the spread of wet rice agriculture."

Yali Xue, Tatiana Zerjal, Weidong Bao, Suling Zhu, Qunfang Shu, Jiujin Xu, Ruofu Du, Songbin Fu, Pu Li, Matthew E. Hurles, Huanming Yang, and Chris Tyler-Smith. "Male demography in East Asia: a north-south contrast in human population expansion times."Genetics 172:4 (April 2006): pages 2431-2439. First published electronically on February 19, 2006. 988 men from 27 populations from China, Mongolia, Korea, and Japan were genetically tested based on their Y chromosomes. The 68 Koreans were divided into two groups: 25 Koreans from China (a place just north of North Korea) and 43 Koreans from "Korea" (South Korea is meant, as the dot on the map on page 2436 shows). Table 1 on page 2434, titled "Haplogroup frequencies in East Asian populations", says the following were the Y-DNA haplogroups of the Korean men from China:
2 had Y*(xA, CE, JR)
3 had C3*(xC3c)
1 had K*
1 had N*
1 had O2*
5 had O2b*
2 had O2b1
6 had O3*(xO3a-O3e)
4 had O3e1*(xO3e1a)
Below were the Y-DNA haplogroups of the Korean men from Korea:
7 had C3*(xC3c)
1 had D
1 had J
1 had K*
1 had NO*/-
1 had N*
1 had O2*
6 had O2b*
6 had O2b1
7 had O3*(xO3a-O3e)
5 had O3e*(xO3e1)
5 had O3e1*(xO3e1a)
1 had P*(xR1a)

Toru Katoh, Batmunkh Munkhbat, Kenichi Tounai, Shuhei Mano, Harue Ando, Ganjuur Oyungerel, Gue-Tae Chae, Huun Han, Guan-Jun Jia, Katsushi Tokunaga, Namid Munkhtuvshin, Gen Tamiya, and Hidetoshi Inoko. "Genetic features of Mongolian ethnic groups revealed by Y-chromosomal analysis." Gene 346 (February 14, 2005): pages 63-70. This includes some Korean Y-DNA samples from Korea and China.

Miroslava V. Derenko, Boris Abramovich Malyarchuk, Tomasz Grzybowski, Galina Denisova, Urszula Rogalla, Maria A. Perkova, Irina Dambueva, and Ilia Zakharov. "Origin and Post-Glacial Dispersal of Mitochondrial DNA Haplogroups C and D in Northern Asia."PLoS ONE (December 21, 2010). Excerpts:

"[...] [The mitochondrial] haplogroup C [...] occurs as rarely as 1-5% in Korea, [...] It is obvious that mitochondrial genomes of Russian, Mansi and FamilyTreeDNA project individual belong to D5a3a branch harboring the entire HVS1 motif, whereas Korean mtDNA represents another D5a3 branch. In fact, this most ancestral sequence indicates that D5a3 lineages could have probably arise in eastern Asia about 16 kya, and that the other lineages, belonging to the D5a3a subgroup participated in a more recent European expansion around 2.6�3.5 kya [...]"

Miroslava V. Derenko, Boris Abramovich Malyarchuk, Galina Denisova, Maria A. Perkova, Urszula Rogalla, Tomasz Grzybowski, Elza K. Khusnutdinova, Irina Dambueva, and Ilia Zakharov. "Complete Mitochondrial DNA Analysis of Eastern Eurasian Haplogroups Rarely Found in Populations of Northern Asia and Eastern Europe." PLoS ONE (February 21, 2012). Excerpts:

"[...] [Mitochondrial] Haplogroup N9a is characteristic of eastern Asian populations, where it is detected at a highest frequencies in Japan (4.6%), China (2.8%), Mongolia (2.1%) and Korea (3.9%) [...] In the current study we have reconstructed the phylogeny of haplogroup N9a based on 59 complete mtDNA genomes [...] Information from complete mtDNA sequencing reveals [...] Khamnigan (Khm_36) and Korean (Kor_87) mtDNAs belong to N9a1, whereas Korean (Kor_92) and Buryat (Br_433) variants can be identified as members of N9a3. [...]"