The question over how these critters made it to South America has spawned all sorts of debates with some arguing that they could have made it to Asia and then across to the Americas, but there's no evidence to support that, Honeycutt says. Others have said they shouldn't be considered rodents at all, but the genetic record shows that their close relatives are in Africa, and definitely are rats. So there it stands. Unless someone comes up with a very different explanation, we're left with a bunch of rats, somehow sailing across the Atlantic, to start a new life and confound scientists years later. You've got to love 'em.
Scientist seeks the answer using genetics.
The thought of a bunch of rats, manning a raft and sailing across the sea, falls a bit short of an adequate scientific explanation.