There is a 4 year old in Great Britain with a tested IQ of 159. She’s right up there with Einstein and Stephen Hawking.
http://www.theblaze.com/stories/could-4-year-old-heidi-hankins-be-the-next-einstein/
It’s actually easier for the very young to score very high on IQ tests.
On the other hand, Marilyn Savant has an IQ of 190, and is nothing more than a columnist for the Sunday inserts.