What causes a helix in nature to appear with either a dextral (”right-handed,” or clockwise) twist or a sinistral (”left-handed,” or counterclockwise) twist is one of the most intriguing ques-
tions in the science of form. Most scientists have maintained that the preferential handedness
of objects such as DNA molecules, protein amino acids, and the shells of snails is due to chance.
For example, Jacques Monod, winner of the Nobel Prize in Physiology or Medicine, attributed
the twist (or ”chirality”) in molecules to the chance selection between two structurally equal
molecules, one dextral and one sinistral. He proposed that the choice of twist occurred when
the first molecule was formed and that this initial choice set the precedent for all subsequent
molecules of that type. However, a new theory challenges the notion that chance is responsible
for the predominance of one type of twist. According to this theory, the chirality found in
molecules, crystals, and shells has its origins in the fundamental chirality of elementary par-
ticles of matter. This theory holds that the universe is fundamentally asymmetric, or chiral,
in that the weak force, one of the four fundamental forces of nature, has a handedness of its
own. The effects of this force are normally observable only at the subatomic level, but they
can be amplified in molecules, crystals, and shells. While the connection between the chirality
of elementary particles and that of macroscopic structures, such as snail shells, is not yet fully
understood, the new theory provides a potential explanation for the prevalence of specific twists
in nature.
