What is the Purpose of the Tusk

There are many different hypothesis' as to why narwhals have a large tusk protruding from their skull. Because  the tusk is a trait that only males have, many theories state that the tusk is a sexual trait that displays male dominance and can attract females through social ranking. Some sources claim that the tusk may be used as a weapon although the most fascinating discovery that has been made regarding the tusk is that it actually contains ten million nerve connections and it may be highly sensitive to many things including hydrodynamics, temperature, pressure, and possibly many other stimuli.