求助OG12-Q68意思~~

The first trenches .....have yielded strong evidence that centrally administered complex societies in northern regions of the Middle East arose simultaneously with but independently of the more celebrated city-states of southern Mesopotamia, in what is now southern Iraq.

麻烦帮忙翻译下意思~~~谢~~~

个人理解：

主语：first trenches,谓语：have yielded，宾语：strongly evidence

宾语从句：主语centrally administered complex societies ，主语状语in northern regions of the Middle East ，谓语arose，谓语副词：simultaneously with 宾语：city-states of southern Mesopotamia，宾语形容词：independently of the more celebrated，状语同位语：in what is now southern Iraq.

我看不出simultaneously with 和independently中间那个but 是转折什么呢。。。。话说这意思还是很混乱。。。