Are you sure neanderthals were bald? I never read that, source?
Why are hunter gatherers of today all fullheads then?
Balding at a young age is really not a modern flaw, the fact that in ancient Egypt, Roman empire, ancient Greece people were balding is mentionned in many writings.
Also people didn't really have a long lifetime expectancy, at 30 you were already considered like an old and wise man back then.To compare, average worldwide lifetime expectancy back in 1950 was 45 years....
Last but not least, some primates suffer aswell from Androgenetic Alopecia, and they were on this planet way before us...so yeah it might be a really old disease
You won't find any sources about neanderthals balding mainly because of the era, prehistory is actually well named, no wrintings back then...and as genetic still doesn't know how to clearly identify all genes involved in Androgenetic Alopecia for sure...well it's basically fucked and most importantly, nobody gives a flying f*** about that and they are right