I've come to the conclusion that hair must be incredibly boring stuff, from a biological point of view. Every single surprising, noteworthy, slightly interesting or even merely unremarkable so-called 'fact' about hair growth seems to be bullshit.
I think we need to get two groups of people in the same room, armed with sharp hairdressing scissors, and let them fight it out:
1) Those who believe merely having already-grown hair still attached to your head consumes resources so cutting it off will conserve them.
2) Those who believe hair follicles know when the end of the non-living protein strand attached to them has been cut off, and so cutting it encourages hair growth.