I have a question regarding how the rules of commas apply in a particular sentence. I cannot seem to work out what rules go with the following excerpt:
The desert savanna of the Neolithic Period, with its flora and fauna, gave way to increasingly arid conditions, and rainfall alone was never adequate for agriculture.
I understand the two independent clauses rule and the interruption rule about making sense if you take out the middle sentence between a pair of commas. This has four clauses, doesn't it? And so what rules should one use here?