Just some scattered things:
I have noticed people talking about their hair falling out on ZC.
It doesn't seem practical that humans would have hair growing over their eyes and eyebrows. Obstruction of vision, irritation of eyes, counter-action of the function of the eyebrows...
In their more primitive state, it would've been difficult for humanoids to cut or tie their hair.
I've seen people talking about hair being used to remove toxins.
Carbohydrates can cause many systems in the body to mess up or go on overdrive.
I can't think of any other animal(unmodified by humans) who's eyes are obstructed by their hair. Even animals who do have increased hair-growth atop their heads such as lions.
Not only head hair, but human facial hair can grow very long, which could cause problems: obstructing consumption of food; breathing; speech, and possibly hosting life which could be detrimental to the human's health. The Vulcher specifically has no hair on it's head, for when it's poking it's head around in carrion.
Humanoids would have had to become good at making cutting tools prior to our hair becoming long and obstructive(when unkempt), for it not to be a major obstruction of life, but why would it become so?
On Raw ZC, would your hair maintain an appropriate length, like your eyebrows, eyelashes etc and thus remove the need for cutting?
I haven't been Raw Carnivorous/ZC long enough to see for myself yet, as whilst improving, other long-term ailments have not yet completely faded. On ZIOH, all long-term male ZCers with pictures have short hair-cuts anyway so that gives me no clues, and I would not feel free enough to post a topic such as this on their forum, it doesn't have the right atmosphere.
Edit: With the bit about 'hair being used to remove toxins', I was thinking along the lines of the possibility of that being why hair may grow so excessively, because it's growing out so many toxins.