Uh 'Most'!?
What!? Amazing to think there was or is any place in earth except say Antarctica where rats were so few and far between that people didn't even know what they looked like.
Have none of them ever read Kenneth Grahame's children's book The Wind in the Willows and seen various drawings and depictions of Ratty?
Strikes me as gross exaggeration and hyperbole, even if they'd never seen a rat in real life (which is pretty hard to believe) then it's even harder to believe they'd never seen a photograph or drawing of one.
For obvious reasons I daren't venture here any further.