@pam69ur,
Anthropologically language and thought probably co-evolved.
But the real question philosophically is the following:
Which can exist without the other?
Language cannot exist without thought. There is no way. But thought can indeed exist without language.
How complex could thoughts be without language? Well, if you took a potential brilliant philosophical genius at infancy, raised him in a room with no features, never let him interact with other humans, never taught him a language, and he survived to adulthood, what could he think? Could he ever generate complex thoughts? Could he understand anything more than the most basic cause and effect relationships?
The thing is that our thoughts are trained and nurtured by interaction with others, chiefly our parents and siblings, but also in school. And language (whether spoken or Braille or sign language or whatever) is the common currency of that growth process.