The DNA found in cells’ mitochondria is passed down from mothers to their offspring. Sequences of such DNA, changing slowly with time, act as a molecular clock. It helps trace back the ancestors of various animals and even their history of domestication.
Based on mitochondrial DNA (mtDNA), sheep are divided into three lineages: A, B and C. Analysing sheep mtDNA sequences, researchers have now revealed that the sheep of lineage A were domesticated in India1. The sheep of lineage B arrived in India via a sea route during ancient trade links with other countries.
This genetic evidence, the researchers say, supports archeological finds that show signs of sheep domestication in greater Indus Valley civilisation around 8,000 years ago.
The scientists from the Central University of Kerala and the Central University of Haryana in India extracted mtDNA from faecal samples of various sheep breeds in India.
The researchers, led by Muniyandi Nagarajan and Satish Kumar, then identified variations at specific non-coding sequences and the cytochrome b gene sequence of sheep mtDNA. Statistical models based on these DNA data revealed that the lineage A was tamed in India.
They found that the mtDNA of lineage B is currently prevalent in two major sheep breeds on the west coast of India. This suggests that the ancestors of those modern sheep on the west coast might have arrived in India through a sea route.
Since domesticated animals are intricately related to agriculture, this study will also help better understand the history of farming, the researchers say.
Kamalakannan, R. et al. Sci. Rep. 11, 19733 (2021) Doi: 1038/s41598-021-97761-y