CASTING DOUBT ON OLD ROCKS' TALES.

The article focuses on a study which shows that billion years old sulfur isotope signature in rocks might not have been caused by an oxygen-poor atmosphere. It notes that the 2.4 billion-year-old geological boundary has always been used to mark Earth's shift to an oxygen-rich atmosphere. It also discusses geochemistry professor Hiroshi Ohmoto and colleagues' study which suggests that the isotope signature were created by chemisorption processes and could be produced in an oxygenated environment.