The following descriptions provide brief overviews of each main mtDNA haplogroup’s origin and geographic distribution.

Haplogroup A

Haplogroup A is found in eastern Eurasia and throughout the Americas. This haplogroup was present in the populations that initially colonized the pre-Columbian Americas, and dates to at least 30,000 years ago. Future work will resolve the issue of how many distinct colonization events there were in the original peopling of the Americas, and the origin and role of individuals bearing haplogroup A.

Haplogroup B

Haplogroup B is found in eastern and southeastern Eurasia and throughout the Americas. This haplogroup was present in the populations that initially colonized the pre-Columbian Americas, and using American samples dates to at least 12,500 years ago. This haplogroup can also be found distributed in Polynesia. Future work will resolve the issue of how many distinct colonization events there were in the original peopling of the Americas, and the role of individuals bearing haplogroup B.

Haplogroup C

Haplogroup C is found in eastern Eurasia and throughout the Americas. This haplogroup was present in the populations that initially colonized the pre-Columbian Americas, and dates to at least 40,000 years ago. Future work will resolve the issue of how many distinct colonization events there were in the original peopling of the Americas, and the role of individuals bearing haplogroup C.

Haplogroup D

Haplogroup D is primarily found in the Americas. This haplogroup was present in the populations that initially colonized the pre-Columbian Americas, and dates to at least 20,000 years ago. Future work will resolve the issue of how many distinct colonization events there were in the original peopling of the Americas, and the role of individuals bearing haplogroup D.

Haplogroup F

Haplogroup F is distributed throughout eastern and southeastern Eurasia. The broad distribution is interesting given the relatively recent origin of this lineage—approximately 10,000 years. Future work will help resolve the processes involved with the recent rapid regional expansion of this lineage.Haplogroup G

Haplogroup H

Mitochondrial haplogroup H is a predominantly European haplogroup that originated outside of Europe before the last glacial maximum (LGM). It first expanded in the northern Near East and southern Caucasus between 33,000 and 26,000 years ago, and later migrations from Iberia suggest it reached Europe before the LGM. It has also spread to Siberia and Inner Asia. Today, about 40% of all mitochondrial lineages in Europe are classified as haplogroup H.

Haplogroup HV

Mitochondrial haplogroup HV is a primarily European haplogroup that underwent an expansion beginning approximately 20,000 years ago. It is more prevalent in western Europe than in eastern Europe, and descendant lineages of the original haplogroup HV appear in the Near East as a result of more recent migration. One of the dominant mitochondrial haplogroups in Europe, haplogroup HV pre-dates the occurrence of farming in Europe. Future work will better resolve the distribution and historical characteristics of this haplogroup.

Haplogroup I

Principally a European haplogroup, haplogroup I is detected at very low frequency across west Eurasia with slightly greater representation in northern and western Europe. Given its wide, but sparse, distribution, it is likely that it was present in those populations that first colonized Europe. This hypothesis is supported by the estimate its age—approximately 30,000 years.

Haplogroup J

The mitochondrial haplogroup J contains several sub-lineages. The original haplogroup J originated in the Near East approximately 50,000 years ago. Within Europe, sub-lineages of haplogroup J have distinct and interesting distributions. Haplogroup J*—the root lineage of haplogroup J—is found distributed throughout Europe, but at a relatively low frequency. Haplogroup J is generally considered one of the prominent lineages that was part of the Neolithic spread of agriculture into Europe from the Near East beginning approximately 10,000 years ago.

Haplogroup K

The mitochondrial super-haplogroup U encompasses haplogroups U1-U7 and haplogroup K. Haplogroup K is found through Europe, and contains multiple closely related lineages indicating a recent population expansion. The origin of haplogroup K dates to approximately 16,000 years ago, and it has been suggested that individuals with this haplogroup took part in the pre-Neolithic expansion following the Last Glacial Maximum.

Haplogroup L

Haplogroup L is a highly diverse haplogroup encompassing many sub-haplogroups, and is generally accepted to be the root haplogroup of all mitochondrial haplogroups. It is in highest frequency in Africa, which is consistent with an origin in Africa. This super-haplogroup dates to approximately 150,000 years, a date which represents the origin of modern humans as inferred from mitochondrial data.

Haplogroup M

The haplogroup M cluster has been characterized as generally of east Eurasia—a geographic region that includes south Asia, east Asia, and Australasia. One of the two deep roots of the mitochondrial tree of haplogroups found in Asia, haplogroup M dates to approximately 70,000 years ago. Interestingly, one of the sub-haplogroups of the M cluster, haplogroup M1, is found primarily in northern Africa, suggesting either a very early divergence from the root of haplogroup M or even migration back to Africa after the original dispersal into Eurasia. Future work will further document the historical distribution of this root haplogroup and closely related haplogroups within the M cluster.

Haplogroup N

The N superhaplogroup has been characterized as pan-Eurasian. Haplogroup N is one of the two major trunks emerging from the original African root, and dates to approximately 65,000 years ago. Interestingly, several sub-haplogroups of the N cluster—haplogroup N1 and derivative lineages—have been detected in the Near East, suggesting either early divergence near the root of haplogroup N or subsequent migrations back towards western Eurasia following the original dispersal into east Eurasia. Future work will further document the historical distribution of this root haplogroup and closely related haplogroups within the N cluster.

Haplogroup R

Emerging from superhaplogroup N, haplogroup R has also been called a superhaplogroup on the basis of its pan-Eurasian distribution, and the fact that it gives rise to many of the major haplogroups distributed across Europe, Asia, and the New World. Haplogroup R dates to approximately 65,000 years ago, a time of key population history events in the peopling of the world by modern humans. Future work will further document the historical distribution of this haplogroup and closely related haplogroups of the R cluster.

Haplogroup T

The mitochondrial haplogroup T is best characterized as a European lineage. With an origin in the Near East greater than 45,000 years ago, the major sub-lineages of haplogroup T entered Europe around the time of the Neolithic 10,000 years ago. Once in Europe, these sub-lineages underwent a dramatic expansion associated with the arrival of agriculture in Europe. Today, we find haplogroup T*—the root haplogroup for haplogroup T—widely distributed in Europe.

Haplogroup U

The mitochondrial super-haplogroup U encompasses haplogroups U1-U8 and haplogroup K. Haplogroup U*, with its own multiple lineages nested within, dates to older than 50,000 years ago. Most likely originating in central Asia, and spreading into Europe in a very early expansion, the presence of haplogroup U* in Europe pre-dates the expansion of agriculture in Europe. Interestingly, individuals with haplogroup U* may have been come in contact with Neanderthals living in Europe at the time.

Haplogroup V

Mitochondrial haplogroup V is a primarily European haplogroup and underwent an expansion within Europe beginning approximately 13,000 years ago. Though it occurs at low frequency throughout Europe, it is interesting to note that the highest frequency of haplogroup V is found among the Saami in Finland and the Catalunya region of Spain. Some evidence suggests that individuals bearing haplogroup V participated in the colonization of Europe following the last period of glaciation. Future work will better resolve the distribution and historical characteristics of this haplogroup.

Haplogroup W

Haplogroup W is derived from the N superhaplogroup, which dates to approximately 65,000 years ago. The origin of haplogroup W dates to approximately 25,000 years ago, and it is mainly found distributed in west Eurasia (or Europe). It is likely that individuals bearing this lineage participated in the expansion into the bulk of Europe following the Last Glacial Maximum. Future work, including obtaining more samples from central Asia, will further refine the historical distribution of this haplogroup and better determine the role it played in the peopling of Europe.

Haplogroup X

Haplogroup X is derived from the N superhaplogroup, which dates to approximately 65,000 years ago. The origin of haplogroup X dates to approximately 30,000 years, and is found distributed throughout the world. Originally found in Europe and thought to be only distributed regionally, the finding of haplogroup X in the Americas startled the human population genetics community. Recently, it has been discovered that there are two major sub-lineages within haplogroup X, and that the geographic distribution and relative ages of these two sub-lineages accord with previous ideas concerning the peopling of the world. Future work on this interesting haplogroup will better document the particulars of the emergence of its distribution and shed more light on regional historical contact and migration.