There are MANY studies out there about brain development and alcohol.
Brain changes significantly after age 18, says Dartmouth research
"The brain of an 18-year-old college freshman is still far from resembling the brain of someone in their mid-twenties," says Bennett. "When do we reach adulthood? It might be much later than we traditionally think."
Well then, other responsibilities and consequences ahould be adjutsed to match the criteria. I would at least like to see some consistency or is that too much to ask.
Another:
Alcohol and the adolescent brain.
While the overall size of the brain increases little beyond early childhood, important structural and functional changes take place as one progresses from childhood to adulthood (Giedd et al., 1999). Recent evidence suggests that, as a result of the changes in brain function that occur during adolescence, alcohol affects adolescents differently than it affects adults.
I was in the military and have heard the argument "Old enough to die for your country but not old enough to drink." Which BTW is as relevant as "Old enough to bleed - Old enough to breed.". There are kids that are 17 in the military and they can't drink. The largest segment of the population that falls victim to binge drinking is 18 - 25 year olds and this is with 18 - 21 year olds doing it illegally, how many more would do it if drinking were legal?