You also have to keep in mind there are racial differences when it comes to average height but when public surveys do their numbers they don't always take ethnic background in to account. As an example, average heights all across Europe have been trending downwards for years but if you look at the heights of only the native populations they have largely stayed the same or increased slightly since WW2.
For a woman of nordic descent 5'8" would be short but if you look at many non Euro south Americans that is really tall for a woman, average height of Guatemalan women is less than 5'.
Anna Marie is a classic southern girl, mostly anglo and french blood, 5'8" is an average height for a woman of her ethnic background.
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Jean's height is harder to pin down because it's changed so much from writer to writer but she was 5'10" in evo and that seems to be the reference design for her in the game so it's a safe bet, she had long legs and was built like a super-model. Given that Jean is from the upper east coast and has natural red hair she is likely a mix of Anglo and irish, which puts her at slightly above average height at 5'10. Storm was the only woman taller than her and Jean wasn't even 18 yet.
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