system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why is the average height so much greater in certain parts of the world? Why aren't people in general about the same height?
gpt
Genetically, almost all have similar potential.

But nutrition plays a big part. Nutrition in them, their parents and even grandparents affects height.

Ever notice that second and third generation immigrants to Western countries are usually a lot taller than their first generation grandparents?