People often seem to think of the world's people as if they can be divided up into three main groups: white, black and yellow. In fact, scientists say it's nonsense because things are really not that simple.

The idea that Africa has only very dark skinned black people ignores the fact that there are many with lighter skins north of the Sahara desert. It also ignores the fact that people from different parts of Africa (while they might all have dark skin) look very different from each other in other ways.

Another example that the 'three different types of people' idea doesn't work is with people from around India. They have dark skin (though it's much lighter in the north, and people in the northern mountains often have blue eyes too) but their faces are very different from Africans. Then there's Australians, who have dark skin but hair like Europeans and Indians. As for Europe, many people in Spain look pretty much like people from north Africa, some Italians are blond and some Norwegians are dark. Confused? Exactly. Genetic differences between people do not fit into neat little boxes that match up to countries. There are no 'pure breeds' of human beings, just lots of blurred edges.

Many people think that people with similar colour skin have similar characteristics. A common example is the achievement of black sportsmen and women and their 'natural rhythm' on the dance floor. This has less to do with biology and more to do with society: black people are not born naturally better at sport and dancing.

Even amongst groups who look pretty much the same, they often have as many genetic differences amongst themselves as they do with some people who look completely different. 'Race' is only skin deep.