's

I have some questions about 's in English compared to other languages. When I've taken Spanish classes before, they would say that a 's (like in "Katie's book") is a "shorcut" that is not in Spanish. I haven't heard about anything like it in languages other than English. It is longer and takes up more space to say "el libro de Katie" and other long phrases with "de" and I think that's one of the reasons why Spanish usually takes up more space than the same thing written in English. So the main questions I have are:

1. Are there benefits to the Spanish way over the English way that make it worth it to spend more time saying the same thing?

2. Are there languages other than English that have equivalents to 's?

3. Are there reasons why English would develop this ability and not other languages or is it just coincidental?

1. Not. It's just the way Spanish evolved.

2. That 's it's a mark of genitive case. So yes, the languages who have genitive case (slavic, turk, romanian, greek ...)

English also has a form similar to Spanish:

"el libro de Katie" = "Katie's book" = "the book of Katie"

книга - book - nominative case
Катя - Katya - nominative case
Кати - Каtya - genetive case ~ 'of Katya'

Книга Кати - the book of Katya

That "s" appears also in scandinavian languages

Yeah I know English has both options, even though people don't usually say "the book of Katie." Spanish only has one option.

Spanish is more analytic , so this leads to longer phrases.

<<Spanish is more analytic , so this leads to longer phrases.>>

No, Spanish is more synthetic than English. Spanish noun however it's indeed more analythic (no cases in Spanish, two cases in English) but it has also markers for genders which English lacks. Better to say Spanish phrases are longer because the words are usually longer (have more syllables).

Spanish phrases are longer because have more words.

<<Are there reasons why English would develop this ability and not other languages or is it just coincidental?>>

As you can see most of the European languages - with the big exception of Western Romance - use genitive. This is not an ability English developed but an archaic trait inherited from Old Germanic.

<<I haven't heard about anything like it in languages other than English.>>

That's because you have studied only languages like Spanish/French. I repeat: most of European languages are like English, using genitive.

If Romance languages were a Latin-Germanic creole, French and Spanish would have preserved the genitive because both Latin and Germanic languages use declensions to express posession. This is a perfect example that illustrates the fact that Romance languages derive from protoItalian or vulgar Latin.

>>If Romance languages were a Latin-Germanic creole, French and Spanish would have preserved the genitive because both Latin and Germanic languages use declensions to express posession. <<

Your argument is moot since the presence of declensions in two languages do not imply that their creole should have them. Romance languages lost their cases at different times (and independent one of another) continuing a tendency already present in Classical Latin (like losing locative case).
So I'm against "Romance languages = Latin-Germanic creole" theory. Usually for a language to change the grammar of another first it needs to have a HUGE impact on the vocabulary which isn't the case here.
Look at Albanian. More than 80 % of vocabulary is borrowed but the grammar is very different than Slavic, Greek, Turkish and Aromanian. It is an almost "pure" albanian grammar. Also Romanian was far more influenced by Slavic than any other Western Romance by Germanic yet the only grammatical influence traceable to Slavic is feminine vocative (almost unused in contemporary language). Another example is Persian grammar very different from arabic one despise the fact that 90 % of words are arabic.
By comparation the Germanic influence over Romance it's almost NONE (apart for a few words). In fact it's the other way around - Romance had a greater influence over Germanic.

Romance languages are so simplified compared to Germanic ones...

Simplified compared to Germanic languages? Like English or Afrikaans?

No, like German, you idiot.