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Details of the research are reported in the 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,” says Andrew Bass, Cornell University 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 says, from their use in flight by birds to swimming by whales and dolphins, and playing piano for humans.

Researchers from Cornell, New York University, and Howard University contributed to the study, which was supported by the National Institutes of Health and the National Science Foundation.

More news from Cornell: www.news.cornell.edu/
More news from NYU: www.nyu.edu/about/news-publications