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{cladogram|title=2009 as per |caption= |clades= }}

Haplogroup

Haplogroup

In the study of molecular evolution, a haplogroup is a group of similar haplotypes that share a common ancestor having the same single nucleotide polymorphism mutation in both haplotypes. Because a haplogroup consists of similar haplotypes, this is what makes it possible to predict a haplogroup...

 R1a is one of the major classifications (called clade

Clade

A clade is a group consisting of a species and all its descendants. In the terms of biological systematics, a clade is a single "branch" on the "tree of life". The idea that such a "natural group" of organisms should be grouped together and given a taxonomic name is central to biological...

s) of Y-chromosome types found in human male lines. It is widespread all across Eurasia

Eurasia

Eurasia is a continent or supercontinent comprising the traditional continents of Europe and Asia ; covering about 52,990,000 km2 or about 10.6% of the Earth's surface located primarily in the eastern and northern hemispheres...

. Many sample studies therefore carry information on the incidence of R1a and/or its subclassifications, in particular the dominant branching line represented by the haplogroups R1a1 and R1a1a.

The table below collates information from a number of such sample studies, with incidence frequencies in sample data reported as percentages, along with the associated sample sizes.