A 1927 study supports a current genetic model for inheritance of human scalp hair-whorl orientation and hand-use preference traits.

The basis of right- vs. left-hand-use preference in humans has been debated for a long time. Culturally learned, birth stress, and biologically specified causes are the prominent etiologies under consideration. A 2003 (Klar 2003) study reported a correlation between a person's preferred hand and the scalp hair-whorl orientation developed on the head. By reinterpreting results of a 1927 (Schwarzburg 1927) study on the genetics of the hair-whorl trait, support for a recent single gene, two-allele "random-recessive model" for both hair-whorl orientation and handedness trait inheritance is demonstrated.