Mystery of elephant's 'sixth toe' solved
A three hundred year old puzzle has finally been solved by researchers at the Royal Veterinary College. When the first elephant was dissected in 1706 by a Scottish surgeon named Patrick Blair, the presence of a bony growth in the feet puzzled the scientific community. While the conventional five toes point forwards and give the elephant it's characteristic tip-toe stance, the 'extra' toe points backwards into the heel pad. Opinion was divided on the growth's purpose, or lack thereof, and the nature of its exact composition.
However, researchers at the Royal Veterinary College led by Professor John Hutchinson used a combination of histology, CT scans, dissection and electron microscopy to investigate. They discovered that the growth is not cartilage as was previously thought, but is instead a highly unusual arrangement of bone. The bone, while not meeting the necessary criteria to constitute a digit in its own right, serves similar purposes as a digit and provides extra support to help spread the elephant's weight. Similar bones have been found in pandas and moles to facilitate climbing and digging respectively.
Professor Hutchinson's research suggests that the presence of the growth is a notable example of evolution in action. "The first elephants appear around 55 million years ago,” he explains. “We looked at early elephants and they had a different kind of foot, which seemed to be quite flat footed and didn't leave much room for this structure underneath. The structure seemed to evolved around 40 million years ago, and it seems to have evolved in concert with elephants getting bigger and more terrestrial and having upright feet, with a more tip-toed foot posture."
RCVS' Mind Matters Initiative (MMI) has launched round two of its veterinary mental health research grants.
