500 mn years old brain reveals evolution of head

London: A new study has identified one of the oldest fossil brains ever discovered - more than 500 million years old - and used it to help determine how heads first evolved in early animals.These fossils originated from the Burgess Shale in western Canada, one of the world's richest source of fossils from the period.

The findings identified a key point in the evolutionary transition from soft to hard bodies in early ancestors of arthropods, group that contains modern insects, crustaceans and spiders. A hard plate, called the anterior sclerite, and eye-like features at the front of their bodies were connected through nerve traces originating from the front part of the brain.

The preserved brains in these fossils have enabled to recognise the anterior sclerite as a bridge between the head of anomalocaridids and that of more familiar jointed arthropods. These ancient brains processed information like in today's arthropods, and were crucial for interacting with the environment, detecting food, and escaping from predators. Since brains and other soft tissues are essentially made of fatty-like substances, finding them as fossils is extremely rare, which makes understanding their evolutionary history difficult.