Construction in a laboratory of a model protocell, which is an artificial supramolecular system that expresses the essential properties of life, would be an important step in identifying the pathway by which life originated1,2. In the 1920s, Oparin3 and Haldane4 independently proposed an origin-of-life scenario, and in the 1930s they claimed that a protocell, i.e., a primitive cell, was a prolifer