We have to take an exam and prove our worthiness to a DMV employee before we are granted the right to get behind the wheel, but once we pass an arbitrary threshold of age we are determined to be 'mature' enough to understand the consequences of alcohol and tobacco with NO test.
We can still keep the age threshold, but grant 'drinking licenses' only to those who are willing to take the exam, which will consist of a few questions about the effects of alcohol, emergency tips, alcohol metabolism, and the history of the temperance movement. At the least this will ensure that one person in a group of drinkers understands what to do in the case of poisoning and save lives.