We are different from each otherbut not as much as you think, and animals aren't necessarily carbon copies. Human's brains are meant to perceive small differences between the organisms of their species, or even just their race. This is also why black people sometimes say all whites look the same, and why white people sometimes say all blacks look the same.
It also has to do with how bad genetics aren't being filtered out as much as other animals as a result of betabux and shit like that.