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R1a-L657
R-L657 is a major South Asian centered branch of R-Z93 and plays an important role in the paternal ancestry of many Indo Aryan speaking populations. Its age suggests that it formed around the time when steppe derived groups were moving into the Indian subcontinent and mixing with local populations. L657's strong presence in northern and northwestern India and Pakistan ties it to demographic processes that followed the Bronze Age steppe expansions into South Asia.
R-L657 occurs at notable frequencies in northern India, especially in the Indo Gangetic plain, and in Pakistan, including Punjabis and some other Indo Aryan associated groups. It is also found in Afghanistan and among South Asian diaspora communities worldwide. Lower frequencies are observed in Iran and Central Asia, reflecting bidirectional contacts between these regions and the Indo Iranian world.
Within R-Z93, L657 is one of several branches that have strong South Asian ties. It contains numerous internal subclades that tend to show local enrichment in particular regions or communities in northern and northwestern India and Pakistan. These subclades provide a fine scale record of founder effects and social structuring over the last few thousand years.
R-L657 is often highlighted in discussions about the genetic impact of steppe migrations in South Asia and their relationship to the formation of Indo Aryan speaking groups. As with other lineages, linguistic and genetic distributions are related but not identical, and L657 lineages can also be found in non Indo Aryan groups due to later admixture.