Left vs Right

BBC News: Sinister secret of snail's escape.

Snails with left-handed shells can have a big advantage in life - predators may find it impossible to eat them.  That is the conclusion of research just published in the Royal Society's journal Biology Letters. Scientists from the US examined whelks and cone shells preyed on by the crab Calappa flammea.  They found the crab is unable to open left-handed shells because it only has a tool for peeling them on its right claw; so it discards them.

Handedness is not just a human trait.  Crabs, shellfish, snails, walruses, it's everywhere, and lefties are always in the minority.  Why is that?

("Sinister" means left in Latin, "dexter" means right.)