Diversity is beautiful but only..

I've been wondering.. Why is it that we in the human family can readily appreciate and embrace diversity in food, flowers, sports, drinks, chocolate, animals and so much more; yet.. When it comes to diversity within our own species.. rather than being appreciated and embraced, diversity seems to stir up fear, distrust, distance and a loud cry for sameness! For me, sameness can be beautiful yet it can also be boring and predictable! I am an identical twin and it didn't take long for my sister and I to grow weary of being "the twins" as we were growing up. "The Twins" was not the fullness of who we were. Yes, we were identical in many ways, and at the same time we were both unique and different. I really want to understand how Diversity can be so beautiful and greatly appreciated in so many areas.. yet when it comes to Being Our Unique Selves.. difference becomes a threat? What are we afraid of?