The reasons were manifold, colonialism, lingering tribal society ...
"Border, Breed Nor Birth"
Dallas McCord Reynolds
However, long before they were strong enough to assert the rights thus granted or to gather intelligence enough for proper group leadership, the new colonialism of the later nineteenth and twentieth centuries began to dawn.
"The Negro"
W.E.B. Du Bois
But his colonialism is only provincialism very articulate.
"Essays"
Alice Meynell