Already, the brain consumed more than a quarter of the body's blood supply... an...

Already, the brain consumed more than a quarter of the body's blood supply... an organ accounting for only a small percentage of body mass. If brains grew larger, and better, then perhaps they would consume more - perhaps so much that, like an infection, they would overrun their hosts and kill the bodies that transported them. Or perhaps, in their infinite cleverness, they would find a way to destroy themselves and each other. There were times when, as he {Stone} sat at State Department or Defense Department meetings, and looked around the table, he would see nothing more than a dozen gray, convoluted brains sitting on the table... Just brains, sitting around, trying to decide how to outwit other brains, at other conference tables.
Idiotic.