Out of Africa

There is evidence that all modern extant human Y chromosomes trace their ancestry to Africa and that the descendants of the derived lineage left Africa and eventually completely replaced previous archaic human Y-chromosome lineages.
Over 400 binary polymorphisms currently describe the Y-chromosome tree. Several mutually reinforcing binary mutations divide the Y-chromosome haplotype phylogeny into two distinctive components, haplogroup A and the remainder of all other haplogroups, specifically B through R.
A and B lineages are restricted to African populations. These lineages are diverse and suggest a deeper genealogical heritage than other haplotypes. Representatives of these lineages are distributed across Africa, but generally at low frequencies.
At least three mutations lie at the root of all the remaining Y-chromosome haplotypes that compose the majority of African and non-African lineages, namely haplogroups C through R (Underhill et al. 2001b).
The mutations that define this node deep within the interior of the Y tree reflect descendants of males who successfully left Africa and formed the scaffold on which all other Y-chromosome diversification with geography has accumulated.
The geographical distribution of this diversification allows us to try to understand some of the major movements that occurred after anatomically modern humans left Africa. The original founders diversified into important lineages that display an irregular geographic distribution.
The majority of Y lineages in the world are composed of a tripartite assemblage consisting of (1) haplogroup C, (2) haplogroups D and E, and (3) overarching
haplogroup F that defines the internal node of all remaining haplogroups G through R. These geographic patterns of genetic affinity and diversification provide insights into the population dynamics associated with migration, population subdivision, fluctuations in population size, and more recent gene flow episodes.
The third major and most peripatetic subcluster of M168 lineages is characterized by at least three mutations (one of which is M89) that define the root of haplogroup F from which all other haplogroups (G through R) deploy.
This F subcluster is suggested to have evolved outside Africa early in the diversification and migration of modern humans. Early Upper Paleolithic peoples throughout Eurasia provide sources from which later populations derive. The differentiation of haplogroup F within Eurasia helps to begin understanding this complex period of the peopling of the world.
The early diversification of a haplogroup F population in Eurasia between 40,000 and 30,000 years ago would have given rise to at least six Y-chromosome populations. Thus, there were multiple independent formations and fragmentations of populations carrying F-related lineages throughout most of Asia, displacing the earlier haplogroup C and D lineages toward the margins.

- Inferring Human History: Clues from Y-Chromosome Haplotypes, P.A. Underhill