According to Albert Bandura's Social Learning theory, and Vygotsky's theory of constructivism, language is a tool of communication that promotes learning in terms of acquiring intelligence, expressing emotions, and analyzing information.
In a culture, any culture, it is through language how you acquire the idiosyncrasies of your culture, the mannerisms that are unique to your heritage and, most importantly, it is through language that you pass on the knowledge, folklore, information, and traditions from one generation to another.
It is a powerful tool that is still studied by cognitive psycholinguists in the way that its intonation or changes in it, produces affect in other people: For instance, a stern tone of voice causes fear at times.
In the Spanish culture, I can tell you a quote that once I heard: "You train dogs in German, You speak to Women in French but you pray to God in Spanish"- Surely that sounds totally biased, but the person who quoted this must have been very keen on the power of language. We are very dependant on our language particularly in our non-verbal language. This is why you may have heard that Spanish people "talk with their hands"- What really happens is that we are very passionate and hot blooded individuals, and we use our entire bodies to convey communication.
This latter is an example of how through language we have conveyed those behavior qualities that make us unique.