Our closest relatives, chimpanzees and bonobos do not generally form fists, and the researchers think they are unable to: when a chimp curls up its fingers it forms a doughnut shape.

BBC: Fighting may have shaped evolution of human hand

The DIs wore their hair long and pinned up in "sock buns, " a Marine Corps specialty that required snipping off the toe line of a sock, rolling the fabric into a doughnut shape, and wrapping and winding a ponytail's worth of hair around it.

WSJ: Acrylic Nails on the Rifle Range