Ancient molecules tied to complex life.

The majority of these molecules, which form in the process of creating modern steroids, were probably produced by eukaryotes, a group that includes animals, plants, protists and fungi, researchers say. Making steroid precursors requires less oxygen and energy than making steroids, which may have let primordial eukaryotes thrive in early Earth's low-oxygen conditions, Brocks and colleagues propose. News Molecular fossils in ancient sedimentary rocks have unveiled a lost world of some of the earliest complex life-forms, which dominated aquatic ecosystems from about 1.6 billion to 800 million years ago. [Extracted from the article]