Alexander the Great is said to have initiated shaved beards to prevent enemy combatants from grabbing hold of the beard with one hand and clobbering with some weapon in the other. Hand to hand combat (especially jaw punching) would be, practically speaking, a third-rate strategy. Weapons aimed to expedite the opponent with a single action requires less energy overall. Since weapons in prehistoric times brought down game animals (according to cave paintings), there is little reason to believe they weren't used in tribal warfare. Some chimps have been observed using clubs in warfare, and dance what appeared to be war dances using clubs. The working hypothesis that beards deflect blows, and therefore had evolutionary value for that reason is open to question, to say the least. A trained warrior would, in any case, go for the nose or the forehead rather than the jaw, using the heel of his hand if no weapon were available.
I am going to say no. It's silly really. The amount of energy absorption from this would be minimal. It could, potentially decrease the chance of sustaining a laceration from a blow. That being said it would be very much used against you. Long hair on any body area is a grip.