Mitochondrial DNA of Black Rats has identified six distinct lineages in the Black Rat's family tree, each originating from a different part of Asia. The six different lineages originated in India, East Asia, the Himalayas, Thailand, the Mekong Delta, and Indonesia. The findings also show a good match between the historic spread of each lineage and ancient routes of human migration and trade. The Black Rat (Rattus rattus) is one of the most common of the world's 56 Rattus species, and is also known as the house, roof or ship rat. It is found throughout Africa, Asia, Australia, Europe and the Americas.