Did life on Earth begin 3.5 billion years ago?
Scientists say they have found proof that life on Earth emerged under harsh conditions more than 3.5 billion years ago—a discovery that, if confirmed, significantly increases the chances that life is commonplace in the universe. UCLA scientist J. William Schopf first claimed back in 1993 that ancient rocks in Western Australia contained “microfossils” of primitive life. But other scientists disputed that finding, arguing that the tiny cylindrical and filamentous shapes he had identified were merely minerals. Now Schopf, working with a team at UCLA and the University of Wisconsin–Madison, says he has proof that the microfossils are the real deal—making them the oldest fossils ever found on Earth, reports SmithsonianMag .com. In a painstaking 10-year process, the researchers found that the ratio of carbon isotopes in each suspected fossil were different from those of the surrounding rock—a clear sign the fossils truly were biological life. Schopf and his colleagues point out that this “primitive and diverse group of organisms” existed before Earth gained an oxygen-rich atmosphere, suggesting that some of them relied on the sun for energy while others thrived on methane. “By 3.465 billion years ago, life was already diverse on Earth—primitive photosynthesizers, methane producers, methane users,” says Schopf. “This tells us life had to have begun substantially earlier.” If primitive life forms could develop under the harsh, oxygen-free conditions of early Earth, Schopf concludes, “life in the universe should be widespread.”
A thin slice of the microfossils