China – Scientists discovered several 520-million-year-old fossilized arthropod brains in China. The finding is the proof that, contrary to the popular belief, that brain tissue do fossilize and it provides new insights on the complex evolution of brains.

Researchers found the fossilized brains of Fuxianhuia protensa, an extinct marine arthropod that lived nearly 520 million years ago, in the fossil-rich region of Chengjiang Shales of Southwest China.

Researchers believe this happened due to covering sandworms and cockroaches in mud, being the brains buried underwater in a mudslide. Credit: Gizmodo

By using an electron microscope, scientists were able to image the brains of the ancient species, analyzing the fossilized tissue that appeared as flattened carbon films. Some of them were laminated with a thin layer of iron pyrite crystals, and their structure is very similar to modern day crustaceans.

Nicholas Strausfeld and his colleagues recreated the process of fossilization on their lab, showing how the brain of the ancient creature was successfully preserved. In order for this process to be completed, the brains must have been buried real quick.

Researchers believe that this happened due to covering sandworms and cockroaches in mud, being the brains buried underwater in a mudslide. As long as the brain remained deep underwater, the neural tissue was safe from any predators and bacteria -the lack of oxygen in the water was an important factor.

But, how these tissues were able to resist the pressure of being underwater, with all that weight? Researchers found the answer in lab experiments, that showed that arthropods brains are highly dense, providing them the ability to sustain under these conditions.

As the sediments were on top of the remains, the pressure probably pushed the water away of the brain cells, causing the tissue to flatten without losing its primary structure. Added to that, the heat and pressure from millions of years of being buried eliminated all the oxygen and hydrogen, leaving behind the mentioned flat carbon film.

Tracking the evolutionary process

Some researchers believe that insects evolved from an ancient arthropod species with a complex brain, the same ancestor from where crustaceans come from. Nevertheless, most scientists think that they come from a clam-like creature, having a simpler brain anatomy, meaning that crustaceans brains have become more complex during the evolutional process.

By examining the Fuxianhuia brain, researchers found that their brain was segmented into three parts, rich with blood vessels. These type of organization is similar to another found in extinct insect species, so this could mean that the brains of arthropods were getting simpler as they evolved. In fact, the human brain is also partitioned into segments.

Another shot at science

Back in 2012, Nicholas Strausfeld, lead author of the paper, presented evidence of brain fossilization. Nevertheless, scientists received the findings with skepticism. They believed that the discovery was a fluke, something that would not repeat again.

However, Strausfeld and his team have now more compelling evidence to study and proof the fossilization and preservation of brain tissue.

“People, especially scientists, make assumptions. The fun thing about science, actually, is to demolish them,” Strausfeld said, according to UPI.

Source: Journal Current Biology