This is where Ichiro Hirao, Shigeyuki Yokoyama and their colleagues at the Yokoyama Cytologic Project in Saitama, Japan, come in.

ECONOMIST: Chemists are trying to synthesise new varieties of life

Before that could happen in a useful way, however, cells would have to be given the machinery to make the ingredients themselves, rather than being spoon-fed them, as Dr Hirao and Dr Yokoyama have done.

ECONOMIST: Chemists are trying to synthesise new varieties of life

When they mixed their artificial biochemicals (including the unnatural amino acid) with a bacterial extract that contained ribosomes and all the appropriate enzymes, Dr Hirao and Dr Yokoyama found that the unnatural additions were treated just like their natural analogues.

ECONOMIST: Chemists are trying to synthesise new varieties of life