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The Discovery Of The Oldest Fossilized Brain In The World Challenges Our Understanding Of Its Evolution

Recent discovery of the oldest fossilized brain that lived and died more than 525 million years ago challenges established ideas about the development of the human brain. This is the first time that a worm-like animal found in rocks in China's southern Yunnan region has been described in such detail.

Daisy-Mae Schmitt
Nov 29, 202265 Shares16164 Views
A recent discovery of the oldest fossilized brainthat lived and died more than 525 million years ago challenges established ideas about the development of the human brain.
This is the first time that a worm-like animal found in rocks in China's southern Yunnan region has been described in such detail. Cardiodictyon catenulumis a tiny animal, measuring in at just 0.5 inches at its longest point, that has been keeping a secret since its 1984 discovery. that a central neurological system, including the brain, is present.
This discovery put an end to a century-long discussion regarding how and why arthropods (the phylum that comprises insects, crustaceans, spiders, and other arachnids, and other lineages such as millipedes and centipedes) developed their complex nervous systems.

A New Theory About Evolution

Scientists have just recently uncovered a brain in the fossilized remains of the 525 million year old Cardiodictyon catenulum, a worm-like creature that was initially discovered in China in 1984. With the use of a process called "chromatic filtering," researchers were able to see the brain and nervous system of a hitherto unsegmented animal. This discovery challenges long-held beliefs about evolution and is quite unusual because of the widespread belief that brains cannot be fossilized.
This anatomy was completely unexpected because the heads and brains of modern arthropods, and some of their fossilized ancestors, have for over a 100 years been considered as segmented.- Nicholas Strausfeld, University of Arizona
A novel hypothesis of evolution is suggested by the lack of segmentation in the head and brain of the Cardiodictyon, which suggests that the brain and trunk nervous system developed independently. It's possible that this finding may shed light on organisms other than insects.

New Theories After Studying The Fragile Nervous System

As an extinct member of the Cambrian era's armored lobopodian family, Cardiodictyonbelongs to a group of creatures currently considered to be completely extinct. The time frame was from around 541 Ma to 485 Ma.
Multiple pairs of soft, stubby legs that lacked the joints of their ancestors, the euarthropods, allowed lobopodians to walk around the sea bottom, according to a news release. The velvet worms found mostly in Oceania, Australasia, and South America are their closest living cousins.
The fossil was so small that x-raying it was problematic. Therefore, "chromatic filtering," using high-resolution digitalized photographs, was utilized to exclude certain colors of the visible spectrum.
A number of unexpected outcomes emerged. They discovered three "confluent domains" in the brain of the animal's unsegmented head and a segmented nervous system in the trunk.

Identifying brain Signatures

The researchers were able to identify a cerebral pattern that has been preserved from the Cambrian period 525 million years ago until the present day by combining their studies of the lobopodian fossils with analyses of gene expression patterns in their living descendants. This combination allowed the researchers to identify the pattern.
Until very recently, the common understanding was 'brains don't fossilize,' so you would not expect to find a fossil with a preserved brain in the first place. This animal is so small you would not even dare to look at it in hopes of finding a brain. We have identified a common signature of all brains and how they formed. We realized that each brain domain and its corresponding features are specified by the same combination of genes, irrespective of the species we looked at. This identifies a common genetic ground plan for making a brain.- Frank Hirth, King's College London

The Results Indicate Continuity

According to Hirth and Strausfled, the implications of their research go beyond only arthropods and might be extended to other kinds of animals as well.
They noted that it might have crucial consequences when comparing the neurological systems of arthropods with those of vertebrates, which display analogous designs in which the forebrain and midbrain are genetically and developmentally different from the spinal cord in the trunk of the animal.
Strausfeld also said that their results might represent a message of continuity, which is encouraging in light of the significant changes that the earth is seeing as a result of changes in climate.
At a time when major geological and climatic events were reshaping the planet, simple marine animals such as Cardiodictyongave rise to the world's most diverse group of organisms – the euarthropods – that eventually spread to every emergent habitat on Earth, but which are now being threatened by our ephemeral species.- Nicholas Strausfeld, University of Arizona

Final Thought

A unifying reason for harmonizing the various morphologies and evolutionary links of the arthropod head and brain has yet to be discovered. In this regard, the preserved neural system of the lower Cambrian lobopodian Cardiodictyon catenulumprovides much-needed context.
Cephalic domains were present prior to the evolution of euarthropod heads and correspond to neuromeres that define living chelicerates and mandibulates, as shown by morphological similarities with stem group arthropods and alignments of homologous gene expression patterns with those of extant panarthropods.
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