If you were right about this; countries never would've fallen apart when the human population was much smaller than it is today, but it happened a lot, so you'r

If you were right about this; countries never would've fallen apart when the human population was much smaller than it is today, but it happened a lot, so you're not. Another thing that disproves this is long lived empires. Japan's been around what like, a millennia and a half? Rome was almost around a thousand years, etc. (Are you gonna argue Japan's a monoculture? Definitely not! https://en.m.wikipedia.org/wiki/Ethnic_groups_of_Japan https://en.m.wikipedia.org/wiki/Ethnic_groups_of_Japan)