THEY are arguably the single greatest scourge of humanity, yet until now little has been known of their origin and historical movement. Black rats, it turns out, colonised the world in four great waves, all associated with human migration or trade.
Ken Aplin at CSIRO Sustainable Ecosystems in Canberra, Australia, and colleagues analysed the mitochondrial DNA of 170 black rats from 76 regions in 32 countries. They also surveyed other species of rat, to probe the animals’ genetic origins. The oldest black rat lineage traces a trail moving from western India 20,000 years ago to the Middle East and from…
