Does someone with 'normal IQ' (85 - 110) have the capability to not only learn but comprehend anything?

Can someone with average intelligence learn and comprehend any topic? (Rocket science, string theory, etc etc)
What inspired this thought:
“Give me a dozen healthy infants, well-formed, and my own specified world to bring them up in and I’ll guarantee to take any one at random and train him to become any type of specialist I might select – doctor, lawyer, artist, merchant-chief and, yes, even beggar-man and thief, regardless of his talents, penchants, tendencies, abilities, vocations, and race of his ancestors. I am going beyond my facts and I admit it, but so have the advocates of the contrary and they have been doing it for many thousands of years.” – Watson