A new study says adulthood starts at 24

I suppose that's one way to look at it.

 

I cant really agree with your example. For one, leaving home and setting out on your own once you reach majority is a western/american cultural phenomenon, and a not very common one at that. In many countries around the world, leaving the home you grew up in if you don't have to simply doesn't happen. In Turkey, family members, even distant family members, tend to live together when possible. Its unusual for a child to leave home just because they reached a certain age. Typically you don't leave home unless/until you get married. In China, you don't even leave home when married if you're a man. You bring your wife to live with you and your parents in their home.

As to intelligence and education, we have enjoyed an average gain of 15 points since the WW2 era. See below:


Being willing to join the military as early as 14 does show admirable courage but it doesn't have anything to do with their development into adults. An argument could even be made that, because they were underdeveloped, they were unable to fully appreciate the danger they were charging into until it was already upon them.

Its fine to despise the current generation of children if you really want to. That's on you. But don't attempt to make an objective argument that they are literally lesser than the children of a few generations previous, because the proof doesn't exist and the logic of such a position is flimsy.

 

If adulthood begins at 24, maybe we should raise the voting age to 24.