By deciphering the genetics in humans and fish, scientists now believe that the neck -- that little body part between your head and shoulders -- gave humans so much freedom of movement that it played a surprising and major role in the evolution of the human brain, according to Cornell and New York University neuroscientists in the July 27 issue of the online journal Nature Communications.

Scientists had assumed that because the fins on fish and the arms on humans seem to be in the same place on the body, the pectoral fins in fish and the forelimbs in humans are innervated (receive nerves) from the same neurons. Not so.

During our early ancestors' transition from fish to land-dwellers, the researchers say, the source for neurons that directly control the forelimbs moved from the brain into the spinal cord, while the torso moved away from the head and became separated by a neck. In other words, human arms, like the wings of bats and birds, became separate from the head and placed on the torso below the neck.

"A neck allowed for improved movement and dexterity in terrestrial and aerial environments," said Andrew Bass, Cornell professor of neurobiology and behavior and one of the paper's authors. "This innovation in biomechanics evolved hand-in-hand with changes in how the nervous system controls our limbs."

This unexpected level of evolutionary plasticity likely accounts for the incredible range of forelimb abilities, Bass said, from their use in flight by birds to swimming by whales and dolphins, and playing piano for humans.

The research, "Ancestry of motor innervation to pectoral fin and forelimb," was authored by Leung-Hang Ma and Robert Baker, both of New York University Langone Medical Center; Edward Gilland of Howard University; and Bass. All four researchers are affiliated with the Marine Biological Laboratory, Woods Hole, Mass. The National Institutes of Health and the National Science Foundation funded the research.