Where does the tradition come from that Noah's sons went separate directions?

I have heard in many places, and was even taught as a child, that Noah's sons, sometime after the Flood, separated and went North, South, and East to repopulate the Earth. The story is commonly used to point out that North, South, and East of where the Ark is said to have settled have three distinct races, which are those of Europe, Africa, and Asia, as this answer mentions and AiG hints on . The issue is that I cannot find this in the Bible. I see the nations that come from Noah's sons listed in Genesis 10, but that doesn't say the sons went in any particular direction. The story of the Tower of Babel follows in Genesis 11, after it is implied that it has been some time since Noah's sons had died. From a Google search I found this very detailed description , but there is no source. Since this doesn't appear to be Biblical, where did this story, or tradition, or theory, come from.