No, it's not biological. People who have been adopted by parents of a different race, and have grown up among people who are of their adoptive parents' race, find that race, not their own, to be the standard. Many studies have shown that it's what you grow up with, not what you are born with, that determines your outlook as far as racial stereotyping. It does, however, come from xenophobia, which has biological roots. It's simply a matter of seeing that someone else is different from you, and distrusting that difference.