Bacteria and Archaea are two of the three domains of life. Both must have evolved from the putative last universal common ancestor (LUCA). One hypothesis is that this happened because the cell membrane in LUCA was an unstable mixture of lipids. Now, scientists from the University of Groningen and Wageningen University have created such a life form with a mixed membrane and discovered it is, in fact, stable, refuting this hypothesis. The results will be published in the journal Proceedings of the National Academy of Sciences in the week of 19 March.