Here is a very interesting and entertaining video about the history of the English possessive. As I was watching the video, I was struck by the close relationship between German and English. Both languages use the possessive, but English did away with complex possessive endings during the late middle ages, along with most other "case" forms, and replaced those cumbersome endings with the apostrophe-'s. Unfortunately, German retained its complex grammar, including the possessive endings, which are part of the Genitive case.
As I have said many a time, learning German is no easy task, and "cases" are a prime example. German has four cases: Nominative, Accusative, Dative, and Genitive. Cases are an important part of German grammar since they dictate the endings of adjectives, indefinite articles, and pronouns.
Look how the word "nett" (which means "nice") has to be contorted depending on the other words in the sentence:
He is a nice person. Er ist ein netter Mensch. (Nominative case with masculine noun)
She is a nice woman. Sie ist eine nette Frau. (Nominative case with feminine noun)
The man gave the dog to the nice young girl.
Der Mann gab den Hund zum netten jungen Mädchen. (Dative case with neuter noun)
Those 12th century English speakers were on to something when they did way those possessive endings!