Why do most girls get less attractive after age 18?

ALmost all girls I know peaked in their beauty from 16-18, then fell off from there, lost their tightness, their skin started to sag, and lost the youthful "glow" that they once had.

Are these girls not taking care of themselves?

it doesn't make sense that a girl would age so much in such a short time.

Age 16

www.barnorama.com/.../02.jpg

Age 20

s-media-cache-ak0.pinimg.com/.../...b738f95f58.jpg

She looks older and not as cute as before
Why do most girls get less attractive after age 18?
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