Do you think prehistoric man's head hair grows constantly throughout

[Conan]

Do you think prehistoric man's head hair grows constantly throughout the course of their lives? Does anyone know? I ask because it's strange that only the hair on our head grows to any length, while the rest stops. I don't believe any other domesticated animal's hair stops growing to any length. Some dogs do maybe? If they do, do any wolves' hair stop growing? If it doesn't, does the wolves' coat naturally degrade by running through forests? If it does, does that mean that prehistoric man scratched its' head against something constantly?