Besides the myth that humans use only 10% of their brain, there has been another myth expressed in this thread. That myth is that since men have larger brains than women, men must be smarter than women. In fact, elephants and most whales have brains that are much larger than any human brain. So it must follow that elephants and whales must be smarter than humans.
In fact, it is the motor function of a larger body that requires a larger brain - not intelligence.
I'd like to know how big Stephen Hawking's brain is. He is not a very large person. I think that my brain is probably larger than his - in fact, when I entered the Army comments were made about my large head. And yet, I wouldn't claim that my intelligence is anywhere close to that of Dr. Hawking.