How did the governmnent or modern society choose 18 as being the age of beginning adulthood?

Question

Is there a scientific explanation? Like its the age when our bodies stop developing.

Answer 1

its because of where most people stop growing, finish puberty and they say our brains stop developing at 21 but they did 18 because people were doing and acting most of the things an older person does and the way they act.

Answer 2

common age for most puberty and all growth to end.

Answer 3

Maybe they figured once you're out of school, you're out of your parents house making your vote for instance less biased. That's kind of what i think it is.  I doubt the government went into any scientific research about it. They probably just picked a number out of a hat :P happy answers !