is the same process male pattern baldness lost, but it stops at some point and stays like that for 10-20 years and sometime, for life..
every man follicle is heavily exposed by dht and is a fact that the temple hairs are thinner than the rest, probably weaker and more susceptible to DHT attack and i think thats the main reason to mature hairline
is said that 95% of men will develop somekind of mature hairline in somepoint of their life
even some thick Norwood 1 hairs have matured at some point from NW0
is very rare to see someone who can keep every single follicle immune to DHT attack, probably those doesnt produce dht enough or have super resistant hair follicles.
you can see that the majority of hairy men/full beard are balding or shows a small recession even if theyill keep the rest of their hair for life, like luis figo who is hairy and have the thickiest hair ever, but clearly shows recession, maybe nw2, but very thick.
and the hairless men often doesnt show any sign of hairloss, because they lack in androgen to attack the follicles, of course there is alot of hairless men balding, but far less than hairy men.
Probably lately in this site the majority of people visiting it are nw2 guys worried about their minor recession and probably half of them ill hold this hairline for life while the others will lose it, it all depends of your inherited genes