Half the people in America are "taller than average"
Because "average" denotes the middle of the scale, half the subjects will be above or below the average point.
I'm constantly amazed to hear guys who are 5ft11 or 6ft say, "and I thought I was tall..." when meeting me because they're about a foot shorter than I am and so many guys are their height.
After thinking about it though, I realized there are enough 5ft9 people half around to tell these six footers how tall they appear to be, so "tall" seems to be quite relative.
Height & Health
Adult height is determined by genetic potential and by net nutrition which is the balance between food intake and the demands on it. Disease makes more nutritional demands on the food we take in, especially in early childhood and thus has a negative impact on overall height.
Historians have made effective use of recorded heights to indicate living standards, in both health and income, for periods where there are few other data. Understanding the determinants of height is also important for understanding health because a wide range of scientific studies find that taller people earn more on average, do better on cognitive tests, and live longer.
Of course these claims only relate to the higher slope of the bell curve and deal with the 90% covered by it - no one has done any extensive research or studies on people in the top 5% of the height curve to see how or when the 'freak factor' sets in and these benefits diminish.
Taller people are thought to live longer because the height-restricting biological responses to childhood nutritional insults and disease seem to have a short-run survival advantage but the consequences of that biological response takes its toll and shorter people are more prone to chronic disease in late life and likely to die earlier.
Taller people seem to earn more on average because of a wide range of factors not the least of which is the positive effects of height bias.
Another important factor is cognitive ability. The cognitive disadvantages of poor nutrition and disease will restrict educational opportunities which influence job prospects and earning potential. --more PNAS research on height-->>
Height affects health over many generations
Super tall or 'extra-tall' people benefit from the cumulative effects of good health & nutrition over 3 to 5 generations. In part, this is because women are born with all of their eggs so by the time she is born, a female's ova are predetermined by prenatal factors.
All of the improvements to a mother's overall health and living condition will improve some factors for her developing foetus and her daughters are likely to be taller than she ever was but still not as tall as their neighbors who didn't suffer poor nutrition or poor health.
It's important to point out that these are issues having to do with metabolism, not genetics and that over time, given consistent access to good nutrition and good health family trees can shake out the short.
My twin sister is just under a foot taller than our great-grandmother and obviously I'm way taller than either of them but many of my male cousins are closer to my height than my great-grandmothers.