  Chirality is not just a structural artifact in biology but it may provide for
a genuine biological advantage. This is due to the phenomenon of chiral
interaction (CI) which is described here for mechanical-chiral devices. The
main mechanical feature of chiral interaction is its mode of selecting one
direction of rotation out of two possible and opposite ones. For example, a
given chiral device such as a rotating water sprinkler, rotates in one
direction. What does rotate in the opposite direction is the mirror of this
given sprinkler. This mode of operation indicates space-time (PT) invariance
which causes it to be also time-irreversible. This also causes a chiral device
to become non-ergodic on microscopic level. This prevents certain chiral
systems from readily reaching thermal equilibrium, and causes the system to act
non-ergodically, which is crucial for living systems as well as for molecular
evolution.
