Hoofing it along, fighting tooth and nail, hanging on by your fingernails—all sorts of everyday sayings recognize that the hard structures at the end of digits are really the same thing, just varying in form. Such structures in biology-speak are called homologues, things that have evolved into different versions, but trace back to a common beginning.
Thus the hooves of horses and the claws of all sorts of creatures evolved from the same source as did our finger and toe nails. These structures, made mostly of a protein called keratin, play a vital role in almost all land-dwelling animals. Not surprising, the nature of these structures are adapted to life styles. A fingernail would be of little use to a horse traversing rough terrain or to a predatory bird grasping prey—yet protect our tender finger ends while allowing the fine manipulations characteristic of humankind.
Admire the lizard as it skitters up a mesquite or the Pronghorn as it
races the wind. Although related only distantly, claw, hoof, and nail affirm the
kinship.
Contributor: Arthur H. Harris, Laboratory for Environmental Biology, Centennial Museum, University of Texas at El Paso.
Desert Diary is a joint production of the Centennial Museum and KTEP National Public Radio at the University of Texas at El Paso.