11 October 2012

Spineless critter had oldest complex brain

Agençe France-Presse
A 520-million-year-old, 7.6-centimetre fossil has yielded evidence that complex brains evolved much earlier than previously thought, say scientists.
Extinct insect fossil oldest complex brain

The fossilised exoskeleton of Fuxianhuia protensa, discovered in China. Credit: Xiaoya Ma

PARIS: A 520-million-year-old, 7.6-centimetre fossil has yielded evidence that complex brains evolved much earlier than previously thought, say scientists.

The preserved external skeleton of Fuxianhuia protensa, an extinct type of arthropod, is the earliest known fossil to show a complex brain, according to a study published in the journal Nature.

“No one expected such an advanced brain would have evolved so early in the history of multicellular animals,” co-author Nicholas Strausfeld, a neurobiologist at the University of Arizona, said in a statement.

Two eyes on stalks with traces of nerve tissue

The fossil was deposited in mudstone during the Cambrian period in what is today China’s southwestern Yunnan Province.

It was a member of the family of arthropods, creatures without backbones, which today include insects, spiders and crustaceans.

The researchers found two eyes on stalks which contained traces of a substance they interpreted to be nerve tissue – optic nerves connected to a three-segment brain.

“This fossil provides the most convincing, and certainly the oldest, description of nervous-system tissue in a fossil arthropod,” Graham Budd of Sweden’s Uppsala University Earth Sciences Department wrote in a comment on the study.

Insect evolution argument settled

He pointed out that soft tissue-like brain matter is much less likely to be preserved in the fossil record than bone and shell as it decayed much more easily.

The team also claimed that their findings settle a long-standing scientific argument about the evolution of insects.

They said their research ruled out branchiopods, shellfish with much simpler brains, as direct ancestors of insects – lumping today’s bugs instead with another arthropod line that includes crabs and shrimp.

“In principle, Fuxianhuia‘s is a very modern brain in an ancient animal,” added Strausfeld.

“It is remarkable how constant the ground pattern of the nervous system has remained for probably more than 550 million years.”

NEWSLETTER

Sign up to our free newsletter and have "This Week in Cosmos" delivered to your inbox every Monday.

>> More information
Latest
issue
CONNECT
Like us on Facebook
Follow @CosmosMagazine
Add Cosmos to your Google+ circles

Get a weekly dose of Cosmos delivered straight to your inbox!

  • The latest in science each week
  • All the updates on our new website launch
  • Exclusive offers and competitions

Enter your name and email address below: