I read a study that attractiveness is when a person's face is closest to the average features of the particular (or target) culture, as well as the more widely-known symmetry effect.
In my experience, "pretty" is separate from popularity. A person can increase or decrease their "pretty". "Pretty" can open and close doors. Maybe more of the former, but the latter can be substantial too.
By 2nd grade I learned who was "attractive" (or not) by NT group standards and was influenced by that. Eventually I learned that wouldn't work for me. Now I am interested in underlying values. My friends today are in all shapes, sizes, colors, and other attributes. I find all of them to be attractive, although I could probably identify the ways in which NT group standards would say otherwise.
Case study #1: I was told at a young age that I was "cute" and then "pretty". I smiled all the time. Which came first? "Pretty" did not make me popular, although it did mean I had to navigate sexual advances (esp. from older men). I downplayed my attractiveness to avoid as much unwanted attention as possible. I was otherwise invisible as many ASD girls are. I could not find friends. I was insecure that way. "Pretty" may have opened doors but those closest to me say it sometimes worked against me too --- people would not approach the (overly) intelligent, attractive woman ---- and I didn't approach them. I noticed that less attractive woman were more readily included in my male-dominated classes and workplaces. It was a very "unattractive" (severe, frowning) woman who made director in a sibling organization.
Case study #2: My ASD BFF knew from a young age that she was not "pretty". She frowned all the time. Which came first? In high school she found a cohort of socially "outside" girls. She was secure that way. In her early late 30s she wanted a relationship and decided maybe she was pretty ... enough. She changed her hairstyle, put aside her drab clothing, added some jewelry, started smiling and -sure enough
- she was "pretty" and she found her partner. She continues those habits to this day. She was and is lovely to me.
Maybe I need to smile less and my male coworkers will take me more seriously. As an engineer, I am often told I am too caring and pretty. Grrrr. Maybe I can say, well it's a shame engineers have a disproportionate amount of uncaring and ugly people.
Open and Close. Ooooooh, wait ------- the NT thing would be to say "I am Pretty and hence powerful, so do as I say..." I really missed the boat on that one.
My children are both "pretty" -- more so than their individual parents (we combined cultures --- created a new average) ---- both my children are ND, but only my daughter is ASD. It will be interesting to see how "pretty" plays out for them.