In college, I took a human evolution class.  One of the things that I learned was that skin color was the easiest genetic traits to change.  Did you know that it only takes 5,000 years for the color of a humans skin to change?  You may be thinking "5,000 years, I'd be dead!"  And you'd be right, however, your decendants wouldn't be.  If you took a family from the equator region and moved them to Sweden, in 5,000 years, their skin color would change to a much lighter shade of brown.

A lot of people might not understand why this would happen.  I'll tell you.  Do you know why people who live close to the equator have dark skin?  It's to protect them from the harmful rays of the sun.  The sun is in more direct contact with the equator for more of the year than anywhere else on the planet.  The farther you are from the equator the less protection you need from the harmful rays of the sun.

Another consequence of living near the equator (or living far from it), is the size of your nose.  Living near the equator is usually warm, living near one of the poles is usually cold.  You're probably thinking "Well Duh".  Now, consider how that affects you physically.  You breath through your nose, right?  The passageways in your nose warm the air that you breath in to get it close to the temperature of your lungs.  If you live in a cold climate, your nostrils will be narrower because then there is more contact with the air to warm it, so it can be closer to the temperature of your lungs.  In warmer climates, you don't need narrow nostrils because the air is almost at that temperature already!

These and many more reasons explain the physical differences between various people around the globe.  But I would like to mention one more thing.  A species is determined to be a species when any two members of that species can produce fertile offspring.  Any two humans can.  Therefore, we are all part of the same species.  Any hatred garnered against anyone else based on color or ethnicity is not based on any differences that matter.