Now that we know much more about ancient exchange and commerce, we know that, because no one aspect of trade was an overriding cause of cultural change or evolution in commercial practices, trade can never be looked on as a unifying factor or as a primary agent of ancient civilization. ( TPO41, 50)

　　overriding adj. 最重要的

　　agent n.动因，成因

　　大家自己先读，不回读，看一遍是否能理解

　　托福阅读长难句分析：

　　(Now that we know much more about ancient exchange and commerce), we know that, (becauseno one aspect of trade was an overriding cause of cultural change or evolution in commercial practices), trade can never be looked on as a unifying factor or as a primary agent of ancient civilization. ( TPO41, 50)

　　这个句子的结构：

　　从句, we know that从句

　　修斯一：(Now that we know much more about ancient exchange and commerce) ，从句

　　中文：由于我们对古代贸易和商业了解了更多

　　修饰二：(because no one aspect of trade was an overriding cause of cultural change or evolution in commercial practices) ，从句

　　中文：因为贸易的任何一个方面都不是商业实践中文化改变或变革的最重要原因

　　托福阅读长难句参考翻译：

　　由于我们对古代贸易和商业了解了更多，我们知道，因为贸易的任何一个方面都不是商业实践中文化改变或变革的最重要原因，所以贸易也不能被当作是古代文明出现的唯一因素或主要动力。

　　这个句子的主要修饰成分就是从句和介词短语，大家务必想清楚，每一个修饰成分修饰的是什么，才能看清楚这个句子的结构。