Oh also, up until I was 24 and moved into an apartment that doesn't get door-to-door salespeople, I would open up the door and immediately get the response, "Is your mommy or daddy home?" I hadn't spoken (and can't speak communicatively), so it couldn't have been tone of voice. I still assume it's something about my default (rather slack) facial expression, but I don't know what exactly it is.
Oh and when I was 25, I was with a 50-year-old autistic woman and someone scornfully looked her up and down and said "What are you, 25?" We both found that rather hilarious.
An example of the opposite: My father, who is also autistic, has looked older than his age for a long time. People always assumed that my brother (also autistic, and 14 years older than me) was my father and that my father was my grandfather. (I'm not sure if the brother as father thing was about him looking older, me looking younger, or both. But I've been told by a former neighbor growing up that I always looked young for my age.)
I do have a bunch of documented minor facial deformities, but they aren't necessarily related to autism any more than a lot of my other physical conditions are, and I doubt they make me look younger.
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"In my world it's a place of patterns and feel. In my world it's a haven for what is real. It's my world, nobody can steal it, but people like me, we live in the shadows." -Donna Williams