User blog comment:Manipulator of Elements/Theory on How We Got Psi Powers/@comment-6829135-20130607212742/@comment-10566514-20130608074006

" I believe since early humans had a smaller brain, they didn't have the part of the brain where the psi is stored and is able to be accessed. If we know that Neanderthals' brains were undeveloped, this would prove my hypothesis that Neanderthals could not use psi."

Smaller cranial capacity = smaller brain.

A smaller brain can lead to the Neanderthal not having the part of the brain where psi is located resulting in the Neanderthal possibly not having psi at all. We, modern humans, and our larger brains possess the ability to manipulate psi to our will.