Human Y-chromosome DNA haplogroup

In human genetics, a human Y-chromosome DNA haplogroup is a haplogroup defined by mutations in the non-recombining portions of DNA from the male-specific Y chromosome (called Y-DNA). Many people within a haplogroup share similar numbers of short tandem repeats (STRs) and types of mutations called single-nucleotide polymorphisms (SNPs).^[2]

The human Y-chromosome accumulates roughly two mutations per generation.^[3] Y-DNA haplogroups represent major branches of the Y-chromosome phylogenetic tree that share hundreds or even thousands of mutations unique to each haplogroup.

The Y-chromosomal most recent common ancestor (Y-MRCA, informally known as Y-chromosomal Adam) is the most recent common ancestor (MRCA) from whom all currently living humans are descended patrilineally. Y-chromosomal Adam is estimated to have lived roughly 236,000 years ago in Africa^{[citation needed]}. By examining other bottlenecks most Eurasian men (men from populations outside of Africa) are descended from a man who lived in Africa 69,000 years ago (Haplogroup CT). Southeast Asia has been suggested as the origin for all non-African human Y chromosomes,^[4] however, this has cited as being unlikely.^[5] Other major bottlenecks occurred about 50,000 and 5,000 years ago and subsequently the ancestry of most Eurasian men can be traced back to four ancestors who lived 50,000 years ago, who were descendants of African (E-M168).^[6][7][8]