These nations generally have more access to high-quality, nutrient-rich diets of meat, fish, and dairy.
Why does height matter?
Height is a biomarker for population health.
Human height is susceptible to stunting with undernourishment, and is one of the most reliable indicators of thriving.
For example, when hunter-gatherers took up farming, heights fell 4-5 inches.
For similar reasons, South Koreans are taller than North Koreans today, even though they've been separated for less than
a century.
In the 19th and early 20th centuries, Americans would have made the top 20 list, but fell off the leaderboard due to the Standard American Diet of grains, seed oils, and sugar.
One straight forward example of what paleopathologists have learned from skeletons concerns historical changes in height. Skeletons from Greece and Turkey show that the
average height of hunger-gatherers toward the end of the ice ages was a generous 5' 9'' for men, 5' 5'' for women. With the adoption of agriculture, height crashed, and by 3000 B. C. had reached a low of only 5' 3'' for men, 5' for women. By classical times heights were very slowly on the rise again, but modern Greeks and Turks have still not regained the average height of their distant ancestors.
— Jared Diamond (1999)