From the simple sundial to the most complex mechanical and digital gadgets, humans have been obsessed with keeping time since appearing on the planet. However, before people were even an inkling of a molecule in the primordial soup, nature has been acting as its own timekeeper. In fact, scientists tap into this system to date events in the earth’s prehistoric timeline.
The method known as radiocarbon dating gets us an approximate timeline. The basic concept is that while alive, organisms absorb radioactive carbon-14 from the atmosphere. Once the organism dies, the carbon-14 starts to decay at a steady rate, allowing scientists to tell how long ago the organism expired. There’s a bit of a hitch, though. The amount of carbon-14 in the atmosphere fluctuates so it was a guessing game about when to start the clock ticking. A way to double check the dates was to refer to other natural markers, like coral and tree rings. With tree rings, the archive is limited to only 12,000 years ago while coral ran into the same carbon-14 problem because it could take years for it to reach the organism and be absorbed.
While nature holds an accurate record she holds tightly to the information. Scientists have just gotten much closer to revealing the secret clock through measurements at the bottom of Lake Suigetsu in Japan. Because the lake has calm waters and the lucky happenstance that plant matter that sinks to the bottom goes from light to dark in winter and summer respectively, radiocarbon dating just got a lot more precise. Through these alternating layers of plant matter, scientists have identified every year back to the Ice Age—and can date to within 10 years only if the sample is between 11,000-53,000 years old. Still pretty impressive and it marks a considerable leap in our understanding of earth’s ultimate timeline.