HOW THE HORSE GOT ITS HOOF
Horses are the masters of tiptoe locomotion. The story goes that, for reasons of speed, strength and lightness, they have gradually lost all but the middle toe over millions of years of evolution. But new research shows it’s more a case of all five digits being rolled into one big one.
It has long been suspected that two splint-like slivers of bone attached to the remaining toe are remnants of the second and fourth digits, and now a detailed study of the fossils of ancestral horses and of the embryological development of modern ones has confirmed this. It has also revealed that bone from the first and fifth digits has been incorporated into the base of the third, where it articulates with the wrist bones.
Meanwhile, the ‘sole’ of the hoof itself is an amalgamation of tissues derived from digits one, two, four and five, and nerves and blood vessels from the “missing” digits are also present.
All in all, the missing toes seem to have been recycled, not discarded.