Frogs, dogs, whales, snails can all do it, but humans and primates can't. Regrow nerves after an injury, that is -- while many animals have this ability, humans don't. But new research suggests that a small molecule may be able to convince damaged nerves to grow and effectively rewire circuits. Such a feat could eventually lead to therapies for the thousands of Americans with severe spinal cord injuries and paralysis. Scientists hope to borrow strategy from simpler animals to repair damaged spinal cord nerves in humans.