>A claim like that needs supporting evidence. I see no reason why segregation among different members of a single community is natural.
Considering that in-group-out-group psychology has been humanity's evolutionary default for tens if not hundreds of thousands of years, I'd say the burden of evidence is on anyone claiming the contrary.
Considering that in-group-out-group psychology has been humanity's evolutionary default for tens if not hundreds of thousands of years, I'd say the burden of evidence is on anyone claiming the contrary.