Scientists once claimed that the races arose in certain regions, due to factors such as sunlight and temperature, then spread slowly outwards. This classic theory is undergoing serious review. Also, the Australian aborigines may carry some older, hominid traits. By 10,000 BC agriculture had developed, and cities began to organize. These grand undertakings may have been conceived in many locations, or migration and trade could have spread that knowledge from a single source.
Theists have reason to prefer the latter.
A new book titled The Genesis Flood puts forth the best theory so far about Noah and the Biblical Flood. It may have been an effect of the most recent Ice Age, during which the Black Sea was a shallow, isolated lake. In 5,600 BC, rising sea levels caused a breach in the Bosporus, allowing sea water to flood its basin. It seems likely that the Indo-European language also originated there. The basin's inhabitants scattered, bringing their knowledge and culture, westwards towards Greece, and east and south into the Middle East.