[mcswell]

English has sometimes been called a creole, i.e. what was a pidgin language but after it has been spoken by several generations of native speakers. One thing it lost some time around the Norman Conquest was the case marking phonology (apart from some pronouns).

[zhengyi13]

I think your point about the loss of case generally stands, but surely the genitive isn't lost?

[mcswell]

True, although it used to be a suffix and now it's (just) a clitic. ("The king of England's crown" would have had the genitive marking on 'king' instead of 'England'.)