I think there is no doubt that women mature physically before men. But I debate their mental maturity. Just because a grown woman doesn't find male humor funny - fart jokes are universally funny to most males - it doesn't mean women aren't immature in other aspects. I don't know the last time there was a group of guys huddled together to gossip about how fat their friends look, or how poorly dressed the new guy is.
A woman might call male humor immature, but it's really because women don't understand men at all. And because they all suffer from superiority complexes, they label naturally exhuberant men as immature. I mean, who really started all this name calling in the first place? If you have any doubt, look at the number of Women's books that complain about men and compare that to the number of Men's books that complain about women. Men aren't the ones complaining and calling names. And yes, name-calling is immature.
Also, you must look at what motivates Men and Women. Women generally don't seek male approval to feel socially acceptable, whereas that's pretty much all that men do think about - getting the girl. Men, on the other hand, don't go around worrying about feeling safe and secure. I mean, when was the last time you said, "I don't think this is safe," to your buddy before he began grinding on his skateboard (or some other equally ridiculous stunt) - after which he fell off the rail and racked his jewels severely. I hope you said never.
And Women will never understand that.