Human Races

I just read a book called Mapping the Human Genome. It looks at genes, languages, cultures and human forms worldwide in an attempt to explain human origins and migrations.They only looked at indigenous people and languages etc. One problem they had was that with travel these days, there has been so much intermixing of races that it is getting harder to distinguish pure indigenous types.They conclude that there are obvious differences between different races which are related to adaptation to climate, Skin colour can be correlated with the intensity of sunlight in certain areas.( White Australians are not adapted to their climate thus skin cancer s high.)Resistance to diseases is also looked at - like malaria and blood groups.The Bushmen of Southern Africa are interesting. They have some Asian characteristics.So I would say that we are all of the same species, but we have become adapted to varying degrees to the different climates we have migrated into over the last 100,000 years or more.

I find it strange that this topic has had so many replies and covered so many different aspects of "race". The original poster simply asked how different human races originated.Firstly a human "race" is poorly defined and probably has no strict scientific definition. But in generally spoken English, it is common to speak of "races" such as the Australian Aboriginal race etc. I suppose in these general terms a race is a group of people who have certain characteristics which are different from other groups of people. Early European settlers in Australia certainly recognised that the Aborigines were different - a different "race".They have evolved to some extent to adapt better to their isolated environment. There are clearly genetic differences between Aboriginals and European settlers. Aborigines cannot digest certain food groups, but seem immune to certain diseases which are prevalent among Europeans. The Aborigines have had about 50,000 years to adapt to their environment.So in summary I believe a "race" is a local variation of the same overall human species. The variations are caused by adaptations to local environments. But we all belong to the one species Homo sapiens.
That is not to say one race is better or worse than another.Due to mixing of races it is often not possible to look at one randomly chosen person and say what "race" he is. But it is possible to investigate "pure" or "near pure" members of a "race" (isolated group) and it will normally be found that they have charactersitics in terms of genetics, language, culture etc which set them apart from surrounding races or groups. Genetic scientists aim to investigate such "near pure " groups to try to unravel the history of mankind.The Kalahari bushmen, pygmies, Australian Aborigines, certain Bedouin tribes are examples of such races or isolated groups.