Haplogroup A is the most basal and diverse of all Y-chromosome lineages. The group is found almost exclusively in Africa, with high representation among hunter-gatherer societies in Ethiopia and Sudan.
Haplogroup B is an ancient lineage distributed sporadically across the African continent. The group is common among pygmy peoples, as well as hunter-gatherer groups. Just over 2% of African Americans belong to this haplogroup.
Haplogroup C originated shortly after the first migration of modern humans out of Africa. Today the group is most common in eastern Eurasia, East and Southeast Asia, and can also be found among western North American indigenous peoples.
Haplogroup D arose in Asia, and its members migrated along the southern coasts of Asia, ultimately settling in Central and East Asia, but not in the Americas. This haplogroup is distinctive in its geographic differentiation.
Haplogroup E is one of the oldest branches of the human family tree. It arose 55,000 years ago, either in East Africa or Asia. During this time, the very first human migrations out of Africa have just occurred. This haplogroup is very common in Africa today, although a particular sub-branch can be found in Europe.
Haplogroup F is an ancient and widespread haplogroup that today comprises more than 90% of all non-African men. Haplogroup F was one of the first haplogroups of modern humans to develop outside of Africa.
Haplogroup G is relatively young but widely distributed, common in Old World European populations, the Middle East, northern Africa, and Central, South, and Southeast Asia. One subgroup, G2c, is a distinctive genetic marker of Ashkenazi Jews.
Haplogroup H is one of the main genetic hallmarks of India, and its members are believed to be responsible for the first major settlements there around 30,000 years ago. Haplogroup H is also prevalent among the Romani people, or Gypsies.
Haplogroup I is found in 20% of European men today, and comprises several subgroups that are associated with specific geographic regions in Europe.
Haplogroup J is very common in the Middle East and the Mediterranean region, including North Africa and southern Europe. The lineage is divided into subgroups J1 and J2, the latter being associated with Neolithic archaeological sites. Haplogroup K spread from its homeland in southwestern Asia throughout Eurasia. Today the lineage ranges from Australia and Oceania to South Asia, and thence to southwestern Asia and North Africa.
Haplogroup L is most prevalent among certain populations of India and Pakistan. The lineage can also be found at lower frequencies in southern Europe, North Africa, the Middle East, and Central Asia.
Haplogroup M is descended from the Eurasian haplogroup K. Haplogroup M is characteristic of Southeast Asian populations, and some have associated it with the development of rice agriculture in that region.
Haplogroup N arose in Southeast Asia, or possibly eastern Eurasia. This haplogroup is distributed somewhat sporadically from China to northeastern Europe, reaching its highest concentrations in certain Siberian populations.
Haplogroup O is specific to East Asia. Its subgroups O1 and O3 are typical of Chinese populations, while O2 is distributed sporadically from South to East Asia.
Haplogroup P and its major descendant groups, Q and R, are represented in many Western Europeans, Indigenous Americans, and Central Asians. Today the descendants of these related lineages can be found throughout Eurasia and the Americas.
Haplogroup Q is common among Siberian native populations. Approximately 15,000 years ago, the lineage spread to the New World, becoming the most widespread patrilineal haplogroup among both North and South American native peoples.
Haplogroup R is a major European haplogroup. Subgroup R1a split off 15,000 years ago, during the peak of the Ice Age. It is found in high frequency and diversity in northern India and eastern Europe. R1b can be found throughout Europe. Recent European emigration has carried this haplogroup to the Americas as well as to Australia.
Haplogroup S is characteristic of the highlands of Papua New Guinea, and researchers believe it may have originated there. Geneticists have only recently distinguished haplogroup S from its parent clade, haplogroup K.
Haplogroup T is a rare haplogroup that is most commonly found in East Africa and Western Asia. It is also found in the central and western Mediterranean regions.