Yale University has been doing research into how social groups interact and I believe that their findings have indicated that fear of the other is a part of our genetic information as part of our survival mechanism. I wonder if these studies are what
AtheistAstroGuy references.
The good news is that, as reasoning beings, we are able to learn how to react differently.
So, according to current theory, we are born with a fear of the unfamiliar and we unlearn it rather than we are born free of prejudices and learn them. If we are born into an inclusive group our sense of inclusion will be reinforced. If the opposite is true our fear of the other will increase.
Here's a reference from NPR I happened across asking myself the same question:
www.nprnews.org/story/2013/08/15/daily-circuit-bias-research