Earth's first animals may have evolved in salty lakes, not oceans, a new study suggests. Evidence for simple life on Earth stretches back billions of years, but the first multicelled animals didn't appear until a few hundred million years ago. Many scientists have argued that these first, complex creatures arose in the oceans. It just seems like a fairly reasonable thing to assume, given the chemical and environmental stability of the oceans," said Martin Kennedy of the University of California, Riverside. But a new study of one of the oldest known fossil beds has revealed abundant amounts of a mineral called smectite, which forms in salty, alkaline lakes—not seawater. Southern China's Doushantuo formation, which dates back 600 million years, contains well-preserved fossil embryos of some of the earliest known animals, including sponges, jellyfish-like creatures, and early forms of a group of extinct corals. At the time those animals lived, fungi and primitive plants had already colonized the land and were gradually increasing the levels of oxygen in the atmosphere. Lakes absorb atmospheric oxygen more readily than the ocean, so early lakes may have become the first hospitable environments for animals, said Kennedy, lead author of the study, appearing in the current online issue of the journal Proceedings of the National Academy of Sciences. [...]