Jack Szostak, a scientist at Harvard Medical School, is trying to build a new kind of life. It will contain no DNA or proteins. Instead, it will based on RNA, a surprisingly mysterious molecule essential to our own cells. Szostak may reach his goal in a few years. But his creatures wouldn't be entirely new. It's likely that RNA-based life was the first life to exist on Earth, some 4 billion years ago, eventually giving rise to the DNA-based life we know. It just took a clever species like our own to recreate it. My cover story in the June issue of Discover has all the details.