Viewed from this evolutionary perspective, the discovery that therapeutic inhibition of poly(ADP-ribosyltransferase) polymerase (PARP) enzymes selectively enhances cytotoxicity in BRCA mutant tumor cells deficient in homologous recombination (60–62) – the novel paradigm of synthetic lethality (63) – merits cautious appraisal (64, 65). The gene discussed is PARP1; the disease is neoplasm.