Haplogroup L (Y-DNA)

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In human genetics, Haplogroup L (M20) is a Y-chromosome DNA haplogroup.

This haplogroup is associated with South Asia. It has also been found at low frequencies among populations of Central Asia, Southwest Asia, and Southern Europe along the coast of the Mediterranean Sea. It is a descendant haplogroup of haplogroup K, and is believed to have first appeared approximately 30,000 years ago.

Haplogroup L is currently present in the Indian population at an overall frequency of ca. 7-15% (Basu et al. 2003, Cordaux et al. 2004, Sengupta et al. 2006, Thamseem et al. 2006). It is especially frequent among Dravidian upper and middle castes (ca. 17-19%), but very rare in Aryan upper and middle castes (ca. 5-6%), which suggests that it may have been (perhaps besides J2) the original Y-haplogroup of the Dravidian creators of the Indus Valley Civilization (Sengupta et al. 2006). Its highest frequency and diversity can be found in western Pakistan/Baluchistan (28%), from where the agricultural creators of this civilization colonized the Indus valley in the 4th millenium BC (Qamar et al. 2002). The presence of haplogroup L is quite rare among tribal groups (ca. 5,6-7%) (Cordaux et al. 2004, Sengupta et al. 2006, Thamseem et al. 2006), which indicates that it was not a Y-haplogroup of the original paleolithic population of India.

Sengupta et al. (2006) recently discovered three subbranches of haplogroup L: L1 (M76), L2 (M317), and L3 (M357). All three are present in Pakistan, but only L1 is regularly found in India. Unfortunately, there seems to be little interest in the origin and distribution of this haplogroup outside India.

An article by O. Semino et al. published in the journal Science (Volume 290, 10 November 2000) reported the detection of the M11-G mutation, which is one of the mutations that defines Haplogroup L, in approximately 1% to 3% of samples from Lebanon, Turkey, Georgia, Greece, Hungary, Calabria, and Andalusia. The sizes of the samples analyzed in this study were generally quite small, so it is possible that the actual frequency of Haplogroup L among Mediterranean European populations may be slightly lower or higher than that reported by Semino et al., but there seems to be no study to date that has described more precisely the distribution of Haplogroup L in Southwest Asia and Europe. Preliminary evidence gleaned from non-scientific sources, such as individuals who have had their Y-chromosomes tested by commercial labs, suggests that most European examples of Haplogroup L might belong to the subclade L2 (M317), which is, among South Asian populations, generally the rarest of the subclades of Haplogroup L.

[edit] Subgroups

The subclades of Haplogroup L with their defining mutation(s), according to the 2006 ISOGG tree:

L (M11, M20, M22, M61, M185, M295) Typical of populations of Pakistan
- L*
- L1 (M27, M76) Typical of populations (especially Dravidian castes) of India and Sri Lanka
- L2 (M317)
  - L2*
  - L2a (M274)
  - L2b (M349)
- L3 (M357)
  - L3*
  - L3a (PK3)

[edit] References

A. Basu et al.: Ethnic India: A Genomic View, With Special Reference to Peopling and Structure. Genome research, 2003, http://www.genome.org/cgi/doi/10.1101/gr.1413403.
R. Cordaux et al.: Independent Origins of Indian Caste and Tribal Paternal Lineages. Current Biology, 2004, Vol. 14, p. 231–235
R. Qamar et al.: Y-Chromosomal DNA Variation in Pakistan. American Journal of Human Genetics, 2002, p. 1107-1124
S. Sahoo et al.: A prehistory of Indian Y chromosomes: Evaluating demic diffusion scenarios. PNAS 2006, www.pnas.org/cgi/doi/10.1073/pnas.0507714103
S. Sengupta et al.: Polarity and Temporality of High-Resolution Y-Chromosome Distributions in India Identify Both Indigenous and Exogenous Expansions and Reveal Minor Genetic Influence of Central Asian Pastoralists. American Journal of Human Genetics, 2006, p. 202-221
I. Thamseem et al.: Genetic affinities among the lower castes and tribal groups of India: Inference from Y chromosome and mitochondrial DNA. BMC Genetics, 2006, http://www.biomedcentral.com/1471-2156/7/42