Thanks for the reply. Let me explain a bit more where I am coming from, and if you still think I am wrong I would love to hear why.
I am speaking with the assumption that culture is basically the shared set of knowledge, values, and behaviors that a group of people hold in common and pass on consciously and unconsciously from one generation to the next. Thus language is a subset of culture. You cannot communicate meaning except that the person to whom you are communicating has been enculturated in the same way as you and agrees with you on the meanings of all the signs and symbols that make up your language. So that is why I think the question here is inseparable from culture.
Your example from Arabic is interesting, but I'm not really sure it fits into the same category as the ones I offered. English speaking cultures do experience kinship relationships and geography, so of course we have ways of expressing this. In fact the relative ease with which you explained what that Arabic name phrase means demonstrates that we can communicate those ideas using the English language and get the meaning across quite well.
One last thing I think I maybe should clarify. I am still a learner in the field of linguistics, and I'm not sure what all is meant by "expressive potential." I did not mean to imply that languages cannot adapt to explain new concepts. If a large group of AAVE speakers were forced into a climate like the Arctic, I would expect their language to make adaptations to communicate a lot more about snow in more efficient ways than they can right now. As the indigenous cultures of the Amazon come into increasing contact with the world around them their language will certainly have to adapt in many ways (as will many other parts of their culture). But the fact is that not all languages adapt at the same time. Even if every language on earth now has a way to describe a motor vehicle, there was a time when they did not. There was a time when some languages were more suited to talked about this object than others (because the speakers of the language never experienced it). So I do not mean that some languages are just worse than others and that is the way it is. But I do mean that at a given point in time (e.g. right now) some languages are better for describing some things. For a more extreme example, imagine the linguistic difficulty of using an isolated language of the Amazon to explain how to remove the engine from a car.
One final example: the Dobu people of Papua New Guinea make (or used to make) annual trading trips with neighboring people groups. One of the most prized items was mwali, a decorative armshell thing. If one of these mwali was put into the hand of a random person on the street in Wisconson and he was asked to describe it to another random person, even a verbose description would probably leave the receptor pretty cloudy on what the object was. But if the same test was done with two Dobu men, they could quickly and easily communicate what the object was and leave the receptor with a very clear idea of what it was. The Dobu language is better at describing this thing because it is experienced by the people who share the Dobu culture. (see Kuehling 2005)