hypothesis thinking is that humans are smart because our distant ancestors were athletic and developed high endurance. This led to greater brain development, better hunting, better eating, more procreating, and so on in an upward evolutionary spiral.
Being in motion made them smarter, and being smarter now allowed them to move more efficiently.
And out of all of this came, eventually, an ability to understand higher math and invent iPads. But that was some time later.
there is a deep evolutionary basis for the relationship between a healthy body and a healthy mind,
NYTimes: Exercise and the Ever-Smarter Human Brain http://nyti.ms/VwBlNv