Within humanity, there is really only one race, the human race. There are different groups of people, however, displaying distinctive characteristics (such, as, those from Europe, those from Africa, and those from the Far East etc.) This distinction is a result of what took place when God scattered mankind over all the earth (after mankind began building a city in the plain of Shinar and began to construct the Tower of Babel.)1
At that time, some who had a genetic tendency towards light skin would have moved into the area we know as Europe etc., some with a genetic tendency towards dark skin would have moved into the area we know as Africa etc. and, those with a tendency towards the characteristics we see in China etc. would have moved into those areas and beyond.
Through genetics, we see the different groups as we do today. Keep in mind that everything one group is, the other is also. All of mankind comes from the same genetic material; we all are descended from our first parents Adam and Eve.2
1 (Genesis 11:1-9)
2 (Genesis 3:20)