When a vertebrate—an animal with a backbone—stubs its toe, electrical signals get carried from the toe to the spinal cord by a nerve, which is made up of bundles of long, fiberlike cells.
Since the researchers couldn’t study a T. rex’s nerves directly, the team looked at how nerves work in a range of modern animals, from the tiny shrew to midsize dogs and pigs to massive Asian elephants.
The scientists found that, for all body sizes, nerves have a basic speed limit of about 180 feet (55 meters) a second. That’s the fastest a signal can travel from an animal’s feet to its spinal cord—the kind of signal that’s essential for walking and running.
At that speed limit, big animals such as elephants can’t run too fast or they’re effectively running blind.
Suppose an elephant steps on a pebble, said study leader Max Donelan of Simon Fraser University in Burnaby, Canada. If the pachyderm was running fast, “its foot would be nearly off the ground before it could do something in response to that troublesome pebble.”