Brains or Biofilm? Doubts Over Famous "Soft Tissue" Fossils

Researchers claimed that brains and other soft tissues were spectacularly preserved in fossils of fuxianhuiids like this little fella for more than 500 million years. But a new study suggests it's all just a bunch of biofilm. (Credit Nobu Tamura) Few things get armchair paleontologists as excited as the phrase "soft tissue preservation." But a new study is casting doubt on some of the most stunning of these finds: Researchers argue that claims of brains, nerves and blood vessels preserved in animals for 520 million years are just a bunch of microbial goo called biofilm. For the last decade, researchers working in Southern China have described a number of fossils from Stage 3 of the Cambrian Period, more than 500 million years ago, with a jaw-dropping degree of preservation. Finding fossils with preserved soft tissue in these rocks was nothing new: the Chengjiang locality, in Yunnan, has long been considered ...