<P> By the early to middle part of the 19th century, British academics believed that the brown rat was not native to Norway, hypothesizing (incorrectly) that it may have come from Ireland, Gibraltar or across the English Channel with William the Conqueror . As early as 1850, however, a new hypothesis of the rat's origins was beginning to develop . The British novelist Charles Dickens acknowledged this in his weekly journal, All the Year Round, writing: </P> <P> "Now there is a mystery about the native country of the best known species of rat, the common brown rat . It is frequently called, in books and otherwise, the' Norway rat', and it is said to have been imported into this country in a ship - load of timber from Norway . Against this hypothesis stands the fact that when the brown rat had become common in this country, it was unknown in Norway, although there was a small animal like a rat, but really a lemming, which made its home there ." </P> <P> Academics began to prefer this etymology of the brown rat towards the end of the 19th century, as seen in the 1895 text Natural History by American scholar Alfred Henry Miles: </P> <P> "The brown rat is the species common in England, and best known throughout the world . It is said to have travelled from Persia to England less than two hundred years ago and to have spread from thence to other countries visited by English ships ." </P>

Why brown rats have been able to thrive in urban areas