Today scientists took another step towards creating the sort of simple life forms that may have been the first inhabitants of Earth. I wrote a feature for the June issue of Discover about this group, led by Jack Szostak at Harvard Medical School. Szostak and his colleagues suspect that life started out not with DNA, RNA, and proteins, but just RNA. This primordial RNA not only carried life’s genetic code, but also assembled new RNA molecules and did other biochemical jobs. Szostak and others have created conditions in their labs under which today’s RNA can evolve into a form able to cary out these primordial tasks. So far, their evolved RNA molecules can assemble short fragments of RNA, using