What's the Single Greatest Asymmetry in the Brain?

The brain is not in some clear way asymmetrical, nor is the skull. On one side it's actually sort of larger in the front and then on the other side it's larger in the back. It was known as Jack of leftian talk after the Jack of left who first described it. And we know that from endocasts of skulls that primitive humans were already showing these asymmetrical enlargements,. although we think they didn't have language.