Scientists have long maintained that brains do not fossilize. However, a new research has provided the strongest evidence yet that it is possible to fossilize the brain. In fact, researchers just identified the brain fossils of a set of 520-million-year-old arthropods.
The species, Fuxianhuia protensa, is an extinct arthropod that roamed the seafloor approximately 520 million years ago. It would have looked something like a very simple shrimp.
‘Scientists had long maintained that brains do not fossilize. But, they just found the brain fossils of a set of 520-million-year-old arthropods that were preserved as flattened carbon films.’
Nicholas Strausfeld, a Regents' professor in the department of neuroscience at the University of Arizona, said, "Each of the fossils found at Chengjiang Shales - fossil-rich sites in southwest China - revealed F protensa's ancient brain looked a lot like a modern crustacean's."
The researchers found that the brains were preserved as flattened carbon films. This led the team to a convincing explanation as to how and why neural tissue fossilizes.
The only way for an object to be fossilized is for it to be rapidly buried. Hungry scavengers cannot eat a carcass if the brain is buried faster and as long as the water lacks in oxygen a buried creature's tissues escapes being consumed by bacteria as well.
The research team suspect F. protensa was buried by rapid, underwater mudslides - a scenario they experimentally recreated by burying sandworms and cockroaches in mud. Strausfeld said, "The brain withstood the pressure from being rapidly buried under thick mud because the nervous system must have been remarkably dense."
In the research paper, Strausfeld and Xiaoya Ma from China's Yunnan University and Gregory Edgecombe from the Natural History Museum in London analyzed seven newly discovered fossils of the same species to find, in each, traces of what was undoubtedly a brain.
Researchers are now working to elucidate the origin and evolution of brains over half a billion years in the past. Strausfeld said, "People, especially scientists, make assumptions. The fun thing about science, actually, is to demolish them."
The study is published in the Current Biology.