Why are people better at distinguishing people of their own racial group and why are animals better at recognising animals of their own species? Why can certain people only recognize certain people. For example, if someone white sees a bunch of African or Asian people, how come it's hard for him to differentiate between them, while they can differentiate between themselves so easily. And the same thing with animals, for example: how come apes can differentiate between themselves, but when I go to the zoo they all look the same. Also since facial recognition is not a thing from the past anymore, does anyone know how much are faces really are different?
The ability of people to better recognise and distinguish faces of their own race has been well studied.

For a general discussion, see Cross-race effect where a range of hypotheses have been proposed.