Bilateral symmetry and the evolution of the brain?

Question

Why was the development of bilateral symmetry in animals an important step in the evolution of a brain?

Answer 1

It wasn't until animals developed bilateral symmetry that a distinct "front" and "back" were established.  Sponges, jellyfish, and other animals that are asymmetrical or radially symmetrical are lacking this.  Once you have a front and back, a concentration of neurons in the front region can occur.  Since you will be encountering environments with your front first, you want to put sense organs and this nerve concentration there.  This is the first stage in the process of cephalization, or the formation of a head with a brain.