A
haplogroup (from the ,
haploûs, "onefold, single, simple" and ), is a group of individual
organisms which, in terms of
molecular evolution, share a
common ancestor – a
genetic line of descent demonstrated by a particular
single nucleotide polymorphism (SNP) mutation. Because a haplogroup consists of similar
haplotypes, it is usually possible to predict a haplogroup from haplotypes. Haplogroups pertain to a single
line of descent, usually dating back thousands of years. As such, membership of a haplogroup, by any individual, relies on a relatively small proportion of the genetic material possessed by that individual. Each haplogroup originates from, and remains part of, a preceding single haplogroup (or
paragroup). As such, any related group of haplogroups may be precisely modelled as a
nested hierarchy, in which each
set (haplogroup) is also a
subset of a single broader set (as opposed, that is, to biparental models, such as human family trees).