Treating hair loss may be as simple as developing therapies to flip a molecular “switch,” according to a new study by researchers from Penn State; the University of California, Irvine; and National Taiwan University.

The researchers reviewed the biological and social evolution of human scalp hair. Based on their analysis, they proposed a novel theory that points to a molecular basis underlying the ability to grow long scalp hair.

In short, human ancestors may have always had the ability to grow long scalp hair, but the trait remained dormant until certain environmental and biological conditions — like walking upright on two legs — turned on the molecular program. The team published their findings, which they said could serve as the basis for future experimental work, in the British Journal of Dermatology.