The big problem, I believe, to understand humanity is to understand the relation between unity and diversity. All human beings have something identical, genetically, anatomically, physiologically, psychologically, and affectively. All human beings, whatever their culture, laugh, cry, smile, but this unity always manifest itself by a difference.
Each individual is different from the others by his character, by his face. Each culture is singular and particular. That's why people say that What differentiates humanity from the animal world is culture, in other words, their knowledge, the language, what is learned, the technique.
But we never see culture. We only know culture through different cultures. Language has, everywhere the same structure, but all languages are different from each other.
Music, we know it through songs. To put it in another way, the human unity has, as treasure, the human diversity, and human diversity has as treasure, the human unity. So, once that is understood, one can, at this moment, understand That, in our world, it's not necessary to want to homogenize and that we are all alike and similar, but, anyway, it's necessary to want to preserve the possibility of having finally a common nation, which is the world nation.
Then, if so desired, there is a complexity problem there also because you're forced to connect the idea of unity and diversity, the similarities and differences, and I believe this is what allows us to establish the correct relations between human beings.