There is a kind of prejudice that is widespread among humans today. If you claim that you at least try to be a moral person, as almost everyone does, you are faced with the question of who will receive your moral treatment. In other words, who has moral status? I suspect that if I polled people across the world on this question they would overwhelming respond that all humans do. The common phrases "this is a human being", "treated like an animal", and "basic human rights" reflect the current paradigm that humans have a higher moral status.
But why should other humans be the only recipients of our moral treatment? What exactly is it about humans that entitles them to this status? If we try to argue that humans have moral status because they behave altruistically, we run into trouble. Worker ants, for example, sacrifice much more for others than humans do. I don't hear much praise of worker ants—presumably because we understand they do this on instinct. We understand they are genetically programmed to aid other ants because they are likely to be from the same colony and carry the same genes.
Perhaps then we should assign moral status to other humans simply because we are closely related. This line of thinking is probably much more common than the former. It's the same line of thinking, however, behind racism. Keep the level of relatedness tight, and you have racism; extend it to include all humans, and you have speciesism. The boundary of the species seems quite meaningless. What does the ability to interbreed have to do with morality?