A paleobotanist dates a fossil layer using radiocarbon and observes that only 12.5% of original C-14 remains. With a half-life of 5730 years, how old is the sample, and what year did it live if the layer was deposited during the Holocene (last 11,700 years)?

Sat, 02 May 2026 14:06:45 +0000

**A paleobotanist dates a fossil layer using radiocarbon and observes that only 12.5% of original C-14 remains. With a half-life of 5730 years, how old is the sample, and what year did it live if the layer was deposited during the Holocene (last 11,700 years)?** When researchers uncover a fossil layer containing ancient organic material, advanced dating techniques offer a window into Earth’s distant past. One such method, radiocarbon dating, reveals how long ago living organisms—including plants preserved in sediment—ceased to exchange carbon with their environment. For a paleobotanist analyzing a layer where only 12.5% of the original carbon-14 remains, the data point becomes a clue: how old is this ancient date of life, and when was it buried? The key to decoding this lies in understanding the half-life of carbon-14—5730 years—a fundamental scientific benchmark. Since the original sample holds just one-eighth of the original C-14, this signals how many half-lives have passed. Each half-life reduces carbon-14 by half: starting at 100%, after one half-life 50%, two make 25%, three bring it to 12.5%. This means the fossil layer is approximately three half-lives old—totaling around 17,190 years. Given that the layer was deposited during the Holocene, the last 11,700 years, this age fits well within established timelines. Radiocarbon dating confirms that such samples typically span the past 50,000 years, though the Holocene’s relatively recent window emphasizes the observer’s current interest in this precise, scientifically rigorous window into prehistory.