The problem with unending hair growth for early humans, is that it would literally trip up our ancestors. This could spell trouble both when running from predators and running in when killing prey.
Indeed, back then, I bet baldness was prized. So too would be hair breakage before the hair gets too long. While both are seen as a problem by some today, they could have literally saved your life back in the stone age.
The one advantage of unending hair growth is that it might take decades to become as long as its person. It could be like an old age pension. If you’re so old that you trip over your hair, then you can stay home and do lesser tasks than hunting. The rest of the clan would have to hunt and forage for you.
So it is my bet, that the first thing that stone tools were developed for, would have been to cut our hair. If you were going back in time to such an era, you could bring along a good pair of scissors. They might be prized over other tools.
I envision the first tools may have been a stone that came to a point. This way, you could put the hair to be cut against flat rock and bash the sharp end of the stone against the hair. This would have been both the first barbershop and the first hair salon.
Only after making the tool to cut hair would we realize it had other uses. Like to kill and skin prey, So I am thinking this may have been the very first tool that humanity made and used, So the first profession after forager might have been the barber or hairdresser.