The Schelling Segregation model (1971) demonstrates how group-level patterns can emerge that are disconnected from the intentions of individuals. In this model, agents are represented by individual red or blue pixels on a Terrain. An agent belonging to each group wants to be surrounded by more of its own type than the other, and will move to an empty cell in the environment if it is in the minority.
These agents do not exhibit aversion to other types of agents per se, and only want to find a position in a non-minority group, but the resulting movements deterministically result in a segregated environment — an illustration of how systems-level effects (i.e. systemic bias) can arise unintuitively from lower-level behavior.