Haplogroup R-M420 (Y-DNA)

Haplogroup R1a
Possible time of origin	22,000 YBP to 25,000 years ago
Possible place of origin	Eurasia (see text).
Ancestor	Haplogroup R1
Descendants	Haplogroup R1a-Z282 (Europe), R1a-Z93 (Asia)
Defining mutations	R1a: L62, L63, L120, M420, M449, M511, M513 R1a1a: M17, M198, M512, M514, M515, L168, L449, L457, L566
Highest frequencies	See List of R1a frequency by population

Haplogroup R1a, or haplogroup R-M420, is a human Y-chromosome DNA haplogroup which is distributed in a large region in Eurasia, extending from Scandinavia, Central Europe and southern Siberia to South Asia.

While R1a originated ca. 22,000 to 25,000 years ago, its subclade M417 (R1a1a1) diversified ca. 5,800 years ago. The distribution of M417-subclades R1-Z282 (including R1-Z280) in Central and Eastern Europe and R1-Z93 in Asia suggests that R1a1a diversified within the Eurasian Steppes or the Middle East and Caucasus region. The place of origin of these subclades plays a role in the debate about the origins of Indo-Europeans.

The SNP mutation R-M420 was discovered after R-M17 (R1a1a), which resulted in a reorganization of the lineage in particular establishing a new paragroup (designated R-M420*) for the relatively rare lineages which are not in the R-SRY10831.2 (R1a1) branch leading to R-M17.

Tatiana et al. (2014) "rapid diversification process of K-M526 likely occurred in Southeast Asia, with subsequent westward expansions of the ancestors of haplogroups R and Q."

The split of R1a (M420) is computed to ca. 22,000, or 25,000 years ago, which is the time of the last glacial maximum. A large, 2014 study by Peter A Underhill et al., using 16,244 individuals from over 126 populations from across Eurasia, concluded that there was compelling evidence that "the initial episodes of haplogroup R1a diversification likely occurred in the vicinity of present-day Iran."

According to Underhill (2014), the downstream R1a-M417 subclade diversified into Z282 and Z93 circa 5,800 years ago. The question of the origins of R1a1a is relevant to the ongoing debate concerning the urheimat of the proto-Indo-European people, and may also be relevant to the origins of the Indus Valley Civilisation. R1a shows a strong correlation with Indo-European languages of western/southern Asia and eastern Europe, being most prevalent in Poland, Russia and Ukraine in Europe and in central Asia, Afghanistan, Pakistan and India in Asia. In Eastern Europe Z282 is prevalent, while in South Asia Z93 dominates. The connection between Y-DNA R-M17 and the spread of Indo-European languages was first noted by T. Zerjal and colleagues in 1999.

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