The study of life’s history on Earth is an ongoing effort to follow the thread further and further back in time. As amazing and fascinating as a few billion years’ worth of fossils are, we still ultimately want that Holy Grail that illuminates the origins of life on Earth. Unfortunately, that goal collides with the fact that the earliest evidence stands the least chance of being preserved through the eons for us to find.

Each new find that purports to supplant the earliest known signs of life is virtually guaranteed to be controversial, subject to poking and prodding from skeptical scientists uncertain that every competing (non-living) explanation can be ruled out. Last August, for example, a paper claimed to show the remnants of stromatolites (small mounds built by communities of shallow water microorganisms) in 3.7 billion-year-old rocks in Greenland. Similar fossils from Australia that come in at about 3.5 billion years old are generally accepted as legit, but anything older is still subject to scientific debate.