The correct answer is: since.
The word “since” is used to indicate a point in time in the past from which something has been happening or continuing. In this case, the point in time is “many years” ago, and the thing that has been happening or continuing is “God has been distributing wisdom among people.”
The other options are not as accurate. The word “for” can be used to indicate a period of time during which something happens or continues. However, in this case, it is not clear what the period of time is. The word “from” can be used to indicate a starting point. However, in this case, it is not clear what the starting point is. The word “so” can be used to indicate a reason or cause. However, in this case, it is not clear what the reason or cause is.
Therefore, the correct answer is “since.”