This is something I have pondered on since I was a kid.
What language do we think in?
I think in some sense humanities first language is that of association,everything in the world seems relative and overlapping.There must have been a time when perception was limited to a blurry whole.Is it not odd that memory and the world at large work much the same,as in relations or associations.Language though is once removed and is an abstract tool,the infinite relations of the world is the stuff of the mind and the first language would be visual.
Today of course we interpret the world in the language of our birth unless otherwise trained.Some people today are yet gifted with a strong ability to visualize the relations of objects in the physical world and to rearrange and manipulate them within their minds,this must have been the first language of all humanity.
There is no doubt the physical world in all its relations is fuel for mind, without which it would self-destruct. Even our dreams are visual representations of objects and often we have symbolic visualizations representations of meaning.So,once more thought is a form of reaction,with all things being relational this reaction had to get more complex,and thus become thought.