[Bounce]

Familiarity,

People trust what looks the same as them(including family and identical twins).

Xenophobia is the sociological phenomenon responsible for distrust between different groups of people, including ethnic & racial biases, based on differences in phenotype/appearance.

You sure? Look at turks and armenians, they look very alike on average, I would say for most it is cultural and religious. Most marry and have children within their (very) small world.