Language is the fundamental trait that sets apart homo sapiens from other animals. The physical ability to generate complex sounds has given us the ability to go beyond instinct.
Culture could not exist without language, and not only because we wouldn’t be able to share it with one another. Animals, lacking full languages, are only able to communicate simple pieces of information: there is food over there; a predator is approaching; I am ready to mate. Contrary to popular belief, they do not chit-chat with one another; they are simply relaying basic information. A cat might indicate to one of its kind that it is happy, but will not seek a full conversation with its fellow. They lack the body parts to do so, and are therefore unable to conceive any higher form of communication. This is not unlinke people who are blind from birth: not having ever seen colors, they simply don’t know what color is. It’s an entirely abstract concept to them, much like every human fails to grasp the concept of a fourth dimension. (I strongly recommend reading Edwin A. Abbott’s “Flatland” to get a better idea of the problem.)