有个问题~~~ 请英语高手 帮我解答下~~~是关于英语语法的问题!

for over the past several million years --> for (over the past several million years)
over the years 固定搭配
over the past several million years：在过去的百万年间里
简单点,你就看成 for the past several million years 好了.over只是强调在那个entire时间段之内都怎么样怎么样.