In the thread Why is ignorance of age not an excuse?, Diogenes the Cynic has made the assertion that no 15 year old can ever be mistaken for a 21 year old:
This is even after multiple people have told him that it does happen (and his own post admits people can mistake 15 year olds for 21, but we’ll ignore that for now).
So I turn to the SDMB, how young can minors get before they’re mistaken for someone past the age of majority? Ancedotes are also encouraged.
Supermodels are usuallly 13 to 15 when they start. Remember the controversy about this 12 year old model?
My friend’s roomate’s sister in college looked perfectly old enough to be a college student - I’d card her now that I’m 30 because everybody looks young but she could have plausibly been 21. She was 13.
Of course they can. I didn’t vote in the poll because I don’t really know what age exactly can be mistaken. But made up correctly and put in nice clothes, certainly teens can look far older, especially if they have mature faces to start with.
The thing is there are a lot of 21-year-olds that look about 15. 21 isn’t terribly old, it’s a young adult. Someone who’s 13-14 is also a young adult. Makeup can do a lot.
At 14 my husband could grow a full beard, and used to frequently buy beer without getting carded (early 90s). I have a picture of myself at 15 looking mid-20s.
And I have always looked about 5 years younger than my age, and my face is still an exceptionally young face. There is no magic guarantee of looking your age.
I coach at the high school level. Plenty of freshman and sophmores who look old enough to be in college.
I based it on the youngest example I’ve met personally: 14.
I voted 12 because I know a girl (granddaughter of a family friend) who looked like she was 18 or 20 when she was 12 (she’s 16 now and still looks to be in her early 20s).
Not sure what the absolute youngest would be, but I always find it interesting when people say things like “X was 12 but looked 18 and was gorgeous…” Aren’t there any normal or ugly people who look old, or do people just not notice them?
Same here, though my answer, chosen thus, was 12. (My cousin…gave her father fits seeing men his age giving her second looks.)
Of course there are. There was a guy I went to school with in junior high who was a grade above me. We never spoke, but he not only looked over 18, he looked like a teacher. And he was ridiculously ugly. His ugliness is what helped him look closer to 40 than 12.
They notice them, they just dont wanna fuck em. 
But seriously, personally I have known a few people that have looked significantly older than they were but not in a “good/pretty” way.
My brother had a 16-year-old girlfriend who could have passed for 35!
I was a perfectly ordinary looking 20 year old, when I was 12. As a young tween/teen I was regularly mistaken for an adult, by adults and other children.
I said 21 in that thread, not 18.
I can’t believe that anyone is saying that 11 and 12 year olds can look 18. What a crock.
Go on then, Dio, remind us of the obvious physical differences between an 18 yr old and a 21 yr old.
Did you read my story in the GD thread about being offered jello shots by the waitress in the sports bar when I was 11? I was 5’8" and had either a B or a C cup by then, I can’t remember. I took it because, hey, free jello! Then my parents, who were paying attention to the game, turned around and saw that I had it and about had a heart attack. I felt bad for the poor waitress–I was probably the only kid inside that place.
Absolutely a minor can look 18 or even 21. I’ve seen 13 year-olds that qualify. Invariably females. I’ve 15- and 16-year old men that look years older, too, but none as young as 13. Note also that the age of majority here is 16, which makes things even more difficult.
I read it. I doubt the waitress thought you were 21.