Languages have commonalities which are built into the brain.
There are various structures and parts of the brain which drive the construction of language. It's a species thing.
And, if one is alone, language does them no good. Language is a way for us to relate to each other, to let us know we exist, and in solitary, with nothing responding to one, they will go nuts.
Language is basic, elemental. Pidgin and creoles have common rules which are consistent over time even though unwritten and unknown to the creators of the language.
Fascinating subject.