By fighting with the forces of nature for thousands of years, humams have achieved more than was ever thought possible.

【翻译】通过千百年来与自然力量的斗争，人类取得的成就要比想象的大。

【分析】

1. 句子的主干是：humams have achieved more

2. than was ever thought possible是带有比较性质的定语从句。因为这种定语从句比较复杂，为了你理解方便，我在than之后加上what，就好理解了。即：than what was ever thought possible。

3. 而what was ever thought possible是名词性从句，意思是“被认为是可能做到的一切事情”，翻译时可引申为“想象到的一切成就”。

4. By fighting with the forces of nature for thousands of years是介词短语，做方式状语，修饰谓语have achieved。