[ConsistentLibertarian]

Places that develop quickly tend to have a lot of outside trade. Greece, for example, after they defeated the Penelopensian (?) navy and become a major trading nation. Europeans have a high degree of cultural variation within a geographical area the size of China. You get cross-pollination through trade, travel, war, etc.

[Apollo]

Europeans have a high degree of cultural variation within a geographical area the size of China.

So does Africa.