Having a head is quite an advantage. Although this may sound banal, it had to be tested in a long evolutionary process: As animal life developed, invertebrates initially dominated the oceans. These had already developed head structures, but the development of a novel, improved head led to the success of vertebrates. This “new head” allowed a wide spatial distribution and multiplication of sensory cells, and thus a much better perception of the environment. This was also essential for the development of a predatory lifestyle.
Click here for original story, Important genetic origin of our senses identified
Source: Phys.org