That is an empirical question, and the historical answer is that that IQ level suffices.
An IQ of 120 is the top ~10%. Here's a 25 year longitudinal study [1] of over 1,500 students that were all in the top 1% and it shows significant differences between the lowest and the highest quartile (who were in the top .01%):
> Ability Differences Among People Who Have Commensurate Degrees Matter for Scientific Creativity > ABSTRACT: A sample of 1,586 intellectually talented adolescents (top 1%) were assessed on the math portion of the SAT by age 13 and tracked for more than 25 years. Patents and scientific publications were used as criteria for scientific and technological accomplishment. Participants were categorized according to whether their terminal degree was a bachelor’s, master’s, or doctorate degree, and within these degree groupings, the proportion of participants with at least one patent or scientific publication in adulthood increased as a function of this early SAT assessment. Information about individual differences in cognitive ability (even when measured in early adolescence) can predict differential creative potential in science and technology within populations that have advanced educational degrees.
This is just one example, but the results seem to be pretty consistent.
[1] https://my.vanderbilt.edu/smpy/files/2013/02/ParkPsychScienc...
Would you be able to send me some more info? Email's in my profile.
He was in a different field, but Richard Feynman's mathematical genius is in dispute by nobody. However his measured IQ is widely quoted at 125.
IQ is somewhat correlated with intelligence, which is somewhat correlated with mathematical ability. You cannot be a mathematician without the mathematical ability. But your ability may or may not get fully reflected on an IQ test.
"Feynman was universally regarded as one of the fastest thinking and most creative theorists in his generation. Yet it has been reported-including by Feynman himself-that he only obtained a score of 125 on a school IQ test. I suspect that this test emphasized verbal, as opposed to mathematical, ability. Feynman received the highest score in the country by a large margin on the notoriously difficult Putnam mathematics competition exam, although he joined the MIT team on short notice and did not prepare for the test. He also reportedly had the highest scores on record on the math/physics graduate admission exams at Princeton. It seems quite possible to me that Feynman's cognitive abilities might have been a bit lopsided-his vocabulary and verbal ability were well above average, but perhaps not as great as his mathematical abilities. I recall looking at excerpts from a notebook Feynman kept while an undergraduate. While the notes covered very advanced topics for an undergraduate-including general relativity and the Dirac equation-it also contained a number of misspellings and grammatical errors. I doubt Feynman cared very much about such things."
http://www.psychologytoday.com/blog/finding-the-next-einstei...
