In human genetics, Haplogroup L (M20) is a Y-chromosome haplogroup.
This haplogroup is associated with India. It is a descendant haplogroup of haplogroup K, and is believed to have first appeared approximately 30,000 years ago.
Haplogroup L is believed to have been associated with the first significant settlement of India. Its arrival may explain a strange phenomenon: prior to the arrival of haplogroup L, the two haplogroups C and D were associated with a great expansion along the southern Asian coast. Today, C is relatively scarce in India, and D is absent. However, the mitochondrial lineages corresponding to the same coastal migration do not show similar declines.
One explanation is that the newcomers from haplotype L may have taken wives from the southern coastal populations (thus preserving the matrilineal line), while killing or driving away their menfolk (thus reducing the frequency of haplotypes C and D).