Most likely earlier Cradle of Civilization?

[Meerkat92]

Water is the major issue there.

You're thinking of Southern California. Up near Oregon, it gets very rainy and wet. Could be a good starting point.

 

[DG Valdron]

Also you need geographical barriers to nomad invasions so any tribe that settles isn't destroyed or pushed out after a time. mountains, and deserts work wonders for these. Which is why egypt, sumer, indus, and china were the first.

Maybe you're looking at it the wrong way. Maybe those barriers weren't against invasion, but against escape.

Consider this approach. You have a rich oasis area supporting a higher than normal population density. The population density gets a little too high... where are those people going to go?

In a relatively rich area, or even an average area, they'll simply vanish off emigrating to the hinterlands.

But if there are no hinterlands to go to, or the hinterlands simply cannot sustain emigration, then the culture has no option but to stick around in the river valley and try to think of something else.

 

[PenguinOverlord]

I have considered this briefly...I think that depending on how close it was to Mesopotamia, it could have affected trade and perhaps cultural interactions. We know that Mesopotamia was nestled between two Rivers, but if the older civilization was perhaps near Greece or Turkey, they could have traded easily. Also, I think that perhaps they would have written language sooner, though influenced by the earlier civilization to make early trade easier.

Interesting Question, though