I loved this article, which I received from NPR today. Linguist Daniel Everett has worked for years with the Pirahã people of the Amazon, and become convinced that culture is the defining shaper of language, rather than some inborn biological structure (take that, Universal Grammar!).
In between, Everett found that the Pirahãs have no words for "please," "thank you," "you're welcome" or "I'm sorry." They have no color words, but instead deploy phrases such as "it is temporarily being immature" for green. They have a limited kinship term system, one that does not distinguish between parent and grandparent or brother and sister. And their sentences lack recursion. This means there are no embedded clauses, as in the English sentence "Bring me the fish that Mary caught."
And this doesn't mean that their language is somehow "primitive." Read the article and learn why. I'm going to be looking forward to seeing more articles in this series.