as long ago as 2650BC 所属时态

OC11th 的31题（124题那本）： Egyptian are credited with having pioneered embalming methods as long ago as 2650BC。是正确答案。解释是credit  x  with的用法。

但此处我想问as long ago as 2650BC跟have pioneered对吗

Longman：

long: 2.at a time that is a long time before or after a particular time

   long ago/since

       He should have left her long ago.

Longman电子辞典蛮好用的，不知道师兄有没有，建议去下载区下载个。

解释的不知道对不对，错误之处还望指正