Tips to improve your spoken Spanish fluency: it involves traveling!
It is an extremely broad topic to cover, and I will certainly not be able to enlighten you in any profound way with just a short blog post.
I can give you an idea, though, about how the linguistic situation in the world changed throughout history until it became what it is today.
Let us look at European languages. Most probably, you have heard of Indo-European languages. Most languages in Europe are actually part of this huge language family.
Due to the migration of peoples, though, what were once big languages divided into smaller languages belonging to the same family. E.g. Balto-Slavic, Germanic, Romance. To this day, we can find similarities in vocabulary between them, even though they are very different from each other.
An interesting thing to note in the evolution of languages is that the vehicle for this evolution are the masses of speakers. I.e. an uneducated person who uses the language in its raw form on an everyday basis has much more influence on the latter than an intellectual does. Basically, it is how the masses speak that determines languages evolution, not the rules that are written in dictionaries and textbooks.
Another fact that you may find intriguing is that the hardest thing to change in any given language is its grammar. If you want to determine the language family of a language, your best bet is to get acquainted with its grammar.
A good example of language evolution are the Slavic languages. Once, Proto-Slavic was spoken by all Slavic tribes on the wide Easter European plane. The scattering of the tribes, though, led to the creation of three languages families: East, West and South Slavic, each containing a number of distinct languages. Their grammar, with the exception of Bulgarian, is similar (e.g. the case system) and their vocabulary contains many parallels.
If you ever decide to delve into this topic, you will find a huge amount of fascinating facts and it will definitely keep you interested to go on. Enjoy!