who has (or had) the biggest I.Q in human history?

Marilyn Vos Savant.

http://www.marilynvossavant.com/

Young Harold Finley taught himself to read, count, and tell time at age 2. Recognized as a genius while still a child, he received a score of 197 on an I.Q. test given to him at age 5. It was the second highest I.Q. score ever recorded at that time. The person with the highest I.Q. was Nathan Leopold, who was later convicted of murdering Bobby Franks. Harold found it ironic that he and Leopold would end up living only miles apart, Harold in Lockport, and Leopold at Stateville Penitentiary.

John

Young Harold Frinely

no1 to be real honest with u. every1 has different focuses with the mind and that's why we need each other 1 person can see the big picture other can do the labor without much that about how. every1 has their own style of IQ and since u never been specific about IQ on what it has to be the answer is every1 for their unique i IQ in their field, unless u rather have it's unknown(cause some ideas were sometimes overshadowed in past).