This chapter shows how the right shift (RS) theory was founded on a comparison of handedness in humans versus nonhumans, in the light of the conclusion of the previous chapter that handedness can best be thought of as a continuum. The paper that first proposed the RS theory was called, “The distribution of manual asymmetry” (Annett, 1972). Several types of distribution were examined, preferences in humans and nonhumans, hand skill for peg moving and handedness in families. The analyses suggested that human handedness is similar to that of other primates and mammals in all but one key respect. The essentials of the argument are that asymmetries depend on accidental differences between the sides that arise during early growth in bilaterally symmetrical organisms. What is specific to humans is a factor that weights the accidental chances in favour of right-handedness. The presence of the RS factor (later RS + gene) does not specify right-handedness, but loads the dice in that direction.