In the tale of The Tower of Babel , all humans used to speak the same language.
Let's build a tower to heaven!!!
Yeah!! We should!!
This wasn't part of God's plan so he got angry at humans.
From now on all of you will speak different languages and I will scatter you across earth!!!
This is a tale that was used to understand or explain why humans speak in different languages. There are many such tales believed by different people. We still do not exactly know how languages came to be but it has definitely developed a lot in these past few centuries.
Travel is a major reason languages have changed so much. People who speak different languages meet and create a bridge between themselves creating new languages.