Bacteria and perhaps other life forms use RNA as environmental sensors
Let's start at the very beginning, several billion years ago, when the first specks of life began to crawl across the barren planet that's now called Earth. There were no cameras to record images of these early life forms, and it's unlikely they left any physical fossils, so it's all but impossible to know much about the primitive organisms. That hasn't stopped scientists from speculating, however. One of the most provocative notions about Earth's first life is that it was far different from that today.