sahara pump造句

• These conditions are responsible for what has been called the Sahara pump theory.
• The Sahara pump theory ( describing an occasionally passable " wet " Sahara desert ) provides one possible explanation of the early variation in the genus " Homo ".
• It also triggered human migration to river valleys, such as from central North Africa to the Nile, which eventually led to the emergence of the societies in the 4th millennium BC . It is associated with the last round of the Sahara pump theory.
• According to the Sahara pump theory evidence suggests that genus " Homo " have migrated out of Africa at least three and possibly four times ( e . g . " Homo erectus ", " Homo heidelbergensis " and two or three times for " Homo sapiens " ).