It's not as hard as you think, and the correlation with nutrition and social class is disappearing and even non-existent in many places. See Japan: https://www

It's not as hard as you think, and the correlation with nutrition and social class is disappearing and even non-existent in many places. See Japan: https://www.japantimes.co.jp/news/2018/02/12/national/science-health/average-height-japanese-born-1980-later-declining-study-finds/ https://www.japantimes.co.jp/news/2018/02/12/national/scienc... There's an increase in low birth rate babies (not due to malnutrition), probably due to increased survivability of smaller more frail babies. The fact that they grow up and lead healthy lives means that their society is indeed selecting for the survivability of smaller people.