[prottog]

Most of the societies you mentioned formed in places with four seasons and winters that you couldn't grow anything in, so you're actually furthering my point. The theory being, of course, that such climates force people to need to prepare to survive through the winter and that forcing function has positive effects on their advancement.

Perhaps it's more accurate to say that this factor is conducive to forming empires, not just cultures. Of the four classical cradles of civilization (China, Egypt, India, Mesopotamia), only half fit this winter criterion, so it's clearly not a prohibitive factor for the formation of a civilization; perhaps just for its technological development and dominion over others.