Haplogroup L (Y-DNA)
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 is somewhat rarer 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 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 millennium 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.
Haplogroup L and Druze: According to DNA testing, Druze are remarkable for their high frequency (35%) of males who carry the Y-chromosomal haplogroup L (M295), which is present in only about 6.4% of the general Arab population of the Middle East.
Early reports (e.g. Wells et al. 2001) of a very high frequency (approaching 50%) of Haplogroup L in South India appear to have been due to extrapolation from data obtained from a sample of 84 Kallars, a Tamil-speaking warrior caste of Tamil Nadu, among whom 40 (approx. 48%) displayed the M20 mutation that defines Haplogroup L. Subsequent studies of various Indian populations have shown this high frequency of Haplogroup L among the Kallars to be an anomaly in the region; Haplogroup L Y-chromosomes rarely comprise even 25% of the Y-chromosome diversity among any Indian population.
Sengupta et al. (2006) recently discovered three subbranches of haplogroup L: L1 (M76), L2 (M317), and L3 (M357). All three are present in Iran and Pakistan, but only L1 is regularly found in India. They make a case for an indigenous origin of L1 in India, by arguing that the spatial distributions of both L1 HG frequency and associated microsatellite variance show a pattern of spread emanating from southern India. By linking haplogroup L1 to the Dravidian speakers, they simultaneously argue for an Indian origin of Dravidian languages. 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.

# 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 Dravidian castes of India and Sri Lanka, with a moderate distribution among Indo-Iranian populations of South Asia
L2 (M317) Found at low frequency in Central Asia, Southwest Asia, and Southern Europe
L2*
L2a (M274)
L2b (M349)
L3 (M357) Found frequently among Burusho and Pashtuns, with a moderate distribution among the general Pakistani population
L3*
L3a (PK3) Found among Kalash
- L*
- L1 (M27, M76) Typical of Dravidian castes of India and Sri Lanka, with a moderate distribution among Indo-Iranian populations of South Asia
- L2 (M317) Found at low frequency in Central Asia, Southwest Asia, and Southern Europe
L2*
L2a (M274)
L2b (M349)
- L2*
- L2a (M274)
- L2b (M349)
- L3 (M357) Found frequently among Burusho and Pashtuns, with a moderate distribution among the general Pakistani population
L3*
L3a (PK3) Found among Kalash
- L3*
- L3a (PK3) Found among Kalash